/ 


.  MOUNTAIN  SPOTTED  FEVER 


S.  BURT  WOLBACH 

BOSTON 


r-rom  the  Laboratories  of  Bacteriology  and  Pathology  of  Harvard  University  Medical 
School  and  the  Pathological  Department  of  the  Peter  Bent  Brigham  Hospital,  Boston) 


Reprinted  from 
Thb  Journal  of  Mboical  Rrsbarch,  Volume  XH. 
No.  1,  pp.  1-197,  November,  1919 


BOSTON 
MASSACHUSETTS 

U.S.A. 


Columbia  Winihtv^itf 
in  tlit  €it]?  of  i^ctu  fSorfe 

CoUegcof  ^fjpfiicmns!  anb  ^urgeonsf 


Reference  I^itirarp 


HXOOO 13064 


\a;' 


STUDIES    ON    ROCKY   MOUNTAIN    SPOTTED    FEVER.* 

S.  Burt  Wolbach,  Boston. 

{From  the  Laboratories  of  Bacteriology  and  Pathology  of  Harvard  University 

Medical  School  and  the  Pathological  Department  of  the  Peter  Bent 

Brigham  Hospital,  Boston.) 

CONTENTS. 

I.     Introduction 3 

II.     Historical  Review      4 

III.  Distribution,  Incidence  and  Mortality 12 

IV.  Clinical  Description       22 

1.  Definition. 

2.  Seasonal  incidence. 

3.  Incubation. 

4.  Symptoms  and  course.     Onset. 

5.  Temperature. 

6.  Pulse  and  respiration. 

7.  Eruption. 

8.  Nervous  symptoms. 

9.  Gastro-intestinal  symptoms. 

10.  The  urine. 

11.  The  blood. 

12.  Complications. 

13.  Types  of  the  disease. 

14.  Treatment. 

V.  Previous  Work  on  the  Pathology 35 

1.  Gross  pathology. 

2.  Microscopic  pathology. 

3.  Attempts  to  demonstrate  a  parasite. 

VI.     Immunity 39 

*  Received  for  publication  July  18,  1919. 


WOLBACH. 

VII.     The  Rocky  Mountain  Spotted  Fever  Tick 40 

I.     Nomenclature. 


The  classification  and  external  anatomy  of  ticks. 

Hosts  of  Dermacentor  venustus. 

Biology  of  Dermacentor  venustus. 

Susceptibility  of  wild   mammals  to   Rocky   Mountain 

Spotted  Fever. 
Infected  ticks  in  nature. 


VIII.     History  and  Identity  of  the  strains  of  virus  used  ....  55 

1.  History. 

2.  The  identity  of  the  strains  used. 

IX.     The   Experimental   Transmission   of   Rocky    Mountain   Spotted 
Fever  by  Ticks 62 

1.  Transmission. 

2.  The  care  and  feeding  of  ticks. 

3.  The  intermittent  feeding  of  adult  ticks. 

X.     Dissection  and  Internal  Anatomy  of  Ticks        67 

1.  The  dissection  of  ticks. 

2.  Internal  anatomy  of  Dermacentor  venustus. 

(a)  The  intestinal  diverticulse. 

(b)  The  Malpighian  tubes. 

(c)  The  salivary  glands. 

(d)  The  female  reproductive  organs. 

(e)  The  brain. 

(/)  The  male  reproductive  organs. 

XI.     Technic 75 

1.  Giemsa  stain  formula. 

2.  Technic  of  making  smear  preparations  from  ticks  and 

animals. 

3.  Histological  technic. 

XII.     The  Parasite 78 

1.  The  parasite  in  mammals. 

2.  The  parasite  in  the  tick. 

3.  The  parasite  in  the  eggs  of  ticks. 

4.  Summary'. 

5.  Nature  of  the  parasite. 

6.  Attempts  at  cultivation. 

XIII.     Experiments  to  prove  the  specificity  of  the  Parasite      .    .  89 

1.  Adult  ticks  proved  to  be  infective. 

2.  Ticks  infected  as  nymphs,  some  of  which  were  proved 

to  be  infective  in  the  adult  stage. 

3.  Control  ticks.     Nymphs  proved   non-infective.     First 

series. 

4.  Control  ticks.     Nymphs  proved  non-infective.     Second 

series. 

5.  Adult  control  ticks,  proved  non-infective. 

6.  Adult  control  ticks,  not  tested. 


ROCKY   MOUNTAIN    SPOTTED    FEVER.  3 

XIV.     Properties  of  the  virus      115 

1.  Filterability. 

2.  Resistance  to  glycerine. 

3.  Resistance  to  bile. 

4.  Resistance  to  dessication. 

5.  Preservation  in  defibrinated  and  citrated  blood. 

6.  Resistance  to  heat. 

7.  Resistance  to  freezing. 

XV.     Rocky  Mountain  Spotted  Fever  in  experimental  animals,       120 

1.  The  disease  in  guinea-pigs. 

2.  The  disease  in  rabbits. 

3.  The  disease  in  monkeys. 

XVI.  Summary  of  the  Patholog>'  in  Man 132 

XVII.  Case  Reports      137 

XVIII.  Summary 179 

XIX.  Bibliography 187 

XX.  Description  of  Plates 193 


I.      INTRODUCTION. 

The  studies  which  have  led  to  this  report  were  undertaken 
at  the  joint  request  of  the  Montana  Department  of  Health 
and  the  Montana  State  Board  of  Entomology.  The  resiilts 
of  original  investigations  have  been  outlined  in  three  brief 
reports  in  the  Journal  of  Medical  Research  (xxxiv,  No.  i ; 
XXXV,  No.  I ;  and  xxxvii.  No.  3).. 

The  purpose  of  this  report  is  to  give  in  detail  the  protocols 
upon  which  the  conclusions  in  regard  to  etiology  are  based 
and  to  describe  the  pathology  of  the  disease.  Because  no 
recent  summary  of  the  many  interesting  and  perplexing 
features  of  the  disease  and  connected  problems  exists,  and 
because  of  the  difficulty  of  access  to  the  early  literature,  I 
have  made  an  effort  to  include  a  comprehensive  review  of 
all  subjects  relating  to  Rocky  Mountain  spotted  fever. 

It  seems  strange  that  this  disease  has  received  so  little 
attention  from  competent  medical  investigators.  Until  the 
brilliant  work  of  Ricketts  it  remained  a  disease  of  mystery, 
and  to  him  belongs  great  credit  for  discovering  the  mode  of 
transmission  and  clearly  outlining  the  work  to  be  pursued 
which  will  lead  to  its  complete  clarification  and  prevention. 


4  WOLBACH. 

The  occurrence  of  the  disease  in  sparsely  settled  moun- 
tainous regions  restricted  to  the  northwest  portion  of  the 
United  States  is  largely  responsible  for  the  lack  of  progress 
towards  its  solution.  It  is  a  disease  which  could  not  be 
studied  in  well-organized  clinics,  and  even  at  the  present 
time  no  complete  clinical  study  has  been  made.  Great  credit, 
however,  is  due  to  the  pioneer  physicians  of  Montana  and 
Idaho  for  accurate  bedside  observations  and  for  their  eager 
cooperation  with  those  who  came  from  a  distance  to  investi- 
gate. 

With  the  increasing  population  of  the  states  afflicted  and 
rising  land  values,  economic  considerations  will  accelerate 
research.  Many  difficult  and  challenging  problems  present 
themselves  for  solution.  The  transmission  by  ticks  explains 
the  seasonal  prevalence  and  gross  distribution  of  the  disease, 
yet  the  maintenance  of  the  virus  in  nature,  its  great  variation 
in  virulence  in  closely  adjacent  regions,  and  its  complete 
absence  in  tick-infested  regions  immediately  adjacent  to  in- 
fected localities  remain  unsolved,  while  the  last  named  is  a 
veritable  puzzle  where  the  contrast  is  so  marked  as  in  the 
case  of  the  east  and  west  sides  of  the  Bitter  Root  Valley. 

II.      HISTORICAL    REVIEW. 

Rocky  Mountain  spotted  fever  has  without  doubt  existed 
in  Idaho  and  Montana  ever  since  the  first  settlements  by 
white  men.  There  is  probable  authenic  information  regarding 
two  cases  which  occurred  in  the  Bitter  Root  Valley  in  1873, 
one  mentioned  by  Wilson  and  Chowning,^^  and  one  by  Stiles.^* 
Neither  Wilson  and  Chowning,  nor  Stiles  could  obtain  evi- 
dence that  the  disease  occurred  among  Indians  prior  to  the 
coming  of  white  settlers.  McCullough,^^  of  Missoula,  Mont., 
writing  in  1902,  says  that  the  Indians  were  subject  to  the 
disease.  He  mentions  the  names  "  black  fever  "  and  "  blue 
disease,"  which  the  early  white  inhabitants  of  the  Bitter 
Root  Valley  applied  to  the  disease.  Michie  and  Parsons^^ 
seem  to  have  been  more  successful  in  tracing  the  occurrence 
back  to  the  Indians.  "  An  old  Indian  chief  of  these  tribes 
[Nez   Perce   and    Flathead],   who    lived    many  years   in    the 


ROCKY   MOUNTAIN    SPOTTED    FEVER.  5 

valley,  tells  us  that  at  certain  times  of  the  year  [spring]  the 
Bitter  Root  Valley  was  visited  by  evil  spirits,  and  that  it 
was  particularly  hazardous  to  visit  certain  canyons  at  this 
time,  as,  for  instance,  Lo  Lo  Canyon.  It  is  now  well  known 
that  tick  fever  appeared  very  soon  after  the  advent  of  the 
first  warm  days  of  spring.  We  also  know  that  there  are 
localities  in  the  valley  which  are  heavily  infected,  —  for 
example,  west  of  Florence.  The  connection  between  facts 
known  at  the  present  day  and  the  statements  made  by  the 
old  Indian  chief  would  indicate  that  the  disease  existed  in 
the  Bitter  Root  Valley  at  least  seventy-five  years  ago.  How- 
ever, there  is  no  authentic  report  of  a  case  so  far  back,  and 
there  are  no  records  of  cases  having  existed  among  the  Indians." 

The  early  history  of  the  disease  is  therefore  seen  to  be 
vague  and  unreliable.  Anderson^  has  tabulated  cases,  some 
reported  by  Wilson  and  Chowning,^^  occurring  in  western 
Montana  from  1885  to  1903,  but  it  is  evident  from  the  scanty 
literature  that  the  disease  was  not  common  enough  to  attract 
much  attention  until  about  1890  to  1895,  or  during  the  first 
period  of  settlement  by  whites.  That  Indians  are  not  immune 
and  occasionally  die  from  the  disease  is  shown  in  the  reports 
collected  by  Fricks^^  from  Wyoming  physicians,  in  which 
numerous  cases  are  recorded,  with  several  deaths,  chiefly 
among  the  Shoshone  Indians. 

The  first  written  account  is  in  the  report  of  the  Surgeon- 
General  of  the  Army  for  1896,  by  W.  W.  Wood,^^  then  major 
and  surgeon.  This  account  contains  no  personal  observations 
by  Surgeon  Wood.  It  contains  data  furnished  by  eight  Idaho 
physicians,  C.  L.  Sweet,  W.  D.  Springer,  R.  M.  Fairchild, 
G.  Collister,  T.  C.  Bowers,  J.  K.  Dubois,  D.  W.  Figgins  and 
H.  Zipf;  and  from  their  descriptions  a  very  fair  account  of 
the  clinical  course  of  Rocky  Mountain  spotted  fever  may  be 
derived.  All  regarded  "  spotted  fever  "  as  a  distinct  disease 
of  unknown  cause.  It  is  of  interest  to  note  that  they  appar- 
ently regarded  the  source  of  the  virus  as  out  of  doors,  and 
the  disease  as  restricted  to  the  spring  months.  Dubois  sug- 
gested the  name  "  exanthesis  rosalia  arthrodynia."  The 
various   appearances   of   the   rash   were  well   described,   and 


6  WOLBACH. 

Bowers  noted  a  "  sanguineous  exudate  "  into  or  beneath  the 
corium.  As  all  the  cases  reported  came  from  Idaho, 
mostly  from  the  neighborhood  of  Boise  and  from  the  Snake 
River  Basin,  the  mortality  was  stated  as  low,  "  very  seldom 
fatal  "  by  Zipf,  two  to  three  per  cent  by  Fairchild,  and  four 
to  five  per  cent  in  old  age  and  one  per  cent  or  less  in  children 
by  Collister. 

In  1899  an  admirable  account  of  "  spotted  fever  "  was 
published  by  E.  E.  Maxey,^^  based  on  cases  occurring  in 
Idaho.  He  defined  the  disease  as  "  an  acute,  endemic,  non- 
contagious, but  probably  infectious  febrile  disease,  charac- 
terized clinically  by  a  continuous  moderately  high  fever, 
severe  arthritic  and  muscular  pains,  and  a  profuse  petechial 
or  purpural  eruption  in  the  skin,  appearing  first  on  the  ankles, 
wrists  and  forehead,  but  rapidly  spreading  to  all  parts  of  the 
body."  Maxey's  account  of  the  signs,  symptoms  and  course 
of  the  disease  remains  one  of  the  best  written.  He  did  not 
mention  the  occurrence  of  cases  in  Montana.  Of  the  pathology 
nothing  was  known  at  that  time.  Under  etiology  he  discussed 
the  seasonal  incidence — -spring  months — -and  the  character- 
istics of  infected  localities,  their  proximity  to  the  mountains, 
streams  and  melting  snow,  and  concluded  that  the  causative 
agent  was  in  the  water  or  soil  over  which  it  ran,  —  a  belief 
still  held  by  inhabitants  who  refuse  to  accept  the  fact  of  tick 
transmission.  Prognosis  favorable,  sums  up  his  estimate  of 
the  mortality  of  the  disease  in  Idaho. 

Although  a  much  more  deadly  type  of  "  spotted  fever  " 
had  been  recognized  for  many  years  in  the  Bitter  Root  Valley, 
the  first  account  of  the  disease  in  that  region  was  published 
in  July,  1902,  by  McCullough^''  (Wilson  and  Chowning's" 
preliminary  report  was  also  published  in  the  same  month). 
His  description  is  brief  and  applies  to  the  more  virulent 
disease  of  the  locality,  and  he  quotes  the  following  series  of 
cases,  one  near  Victor  of  sixteen  cases  with  twelve  deaths, 
one  near  Stevensville  of  forty  cases  with  thirty  deaths,  and 
his  own  experience  with  thirty-six  cases  in  a  period  of  twelve 
years  with  a  mortality  of  seventy-five  per  cent. 


ROCKY    MOUNTAIN    SPOTTED    FEVER.  7 

At  this  date,  1902,  the  disease  was  recognized  in  Montana 
as  a  serious  obstacle  to  the  settlement  of  valuable  agricultural 
lands  in  the  Bitter  Root  Valley.  There  was  complete  igno- 
rance of  all  factors,  except  that  of  season  and  locality,  regarding 
transmission.  Water  from  melting  snow  and  the  rotting  saw- 
dust of  lumber  camps  were  supposed  to  carry  and  engender 
the  cause  of  the  disease.  Physicians  dreaded  the  care  of 
cases  because  of  their  absolute  helplessness  in  treatment, 
and  the  settlers  because  of  the  deadly  and  mysterious  nature 
of  the  disease. 

The  first  serious  investigation  was  begun  in  this  year  by 
Wilson  and  Chowning,^^  vho  were  engaged  by  Dr.  H.  F. 
Longeway,  Secretary  of  the  Montana  State  Board  of  Health, 
"  to  investigate  the  nature,  causation  and  means  of  prevention 
of  the  disease,"  and  their  work,  while  leading  to  some  erroneous 
conclusions  as  to  etiology,  contributed  many  valuable  facts, 
particularly  as  to  pathology  and  epidemiology,  and  furnished 
provocative  stimulus  for  subsequent  research.  They  ob- 
tained records  of  one  hundred  and  twenty-six  cases  with  a 
mortality  of  eighty-seven  per  cent,  and  made  the  first  post- 
mortem examinations  and  study  of  the  blood  during  life. 
They  called  attention  to  the  occurrence  of  the  disease  in 
Nevada  and  Wyoming.  Most  important,  however,  was  their 
conclusion  that  the  disease  is  transmitted  by  the  wood  tick 
of  the  locality,  then  identified  as  a  new  species  of  Dermacentor 
by  Stiles.  This  conclusion  was  based  partly  upon  shrewd 
and  sound  observations  of  individual  case  histories  and  the 
epidemiology  of  the  disease,  and  upon  the  finding  of  a  supposed 
intracorpuscular  protozoan  parasite,  a  Piroplasma  identified 
as  similar  to  that  known  to  be  the  cause  of  Texas  fever  in 
cattle  and  transmitted  by  a  tick.  Their  illustrations  depict 
bodies  unlike  any  known  inclusion  or  artefact  in  human 
blood,  and  convincingly  similar  to  known  types  of  Piroplasma, 
or  Babesia,  yet  this  part  of  their  work  did  not  prove  valid 
and  their  findings  are  still  unexplained.  This  "organism" 
was  named  by  them  "  Pyroplasma  hominis  "  and  the  disease 
"  Pyroplasmosis  hominis."     Similar  parasite-like  bodies  were 


O  WOLBACH. 

seen  by  them  in  the  blood  of  the  burrowing  squirrel  or  ground- 
squirrel,  Sphermophilus  (Citellus?)  columhianus ,  and  this 
animal  was  accordingly  regarded  as  a  third  host  of  "  Pyro- 
plasma  hominis''  —  a  supposition  in  accordance  with  dis- 
tribution, seasonal  habits  and  tick-host  capacity  of  the  burrow- 
ing squirrel.  They  made  experimental  inoculations  into 
pigeons  and  rabbits,  and  found  in  the  blood  of  the  latter  the 
piroplasma-like  bodies.  They  noted  little  in  the  way  of 
disease  symptoms  in  the  rabbit,  but,  as  enlargement  of  the 
spleen  was  found  in  two  which  were  autopsied,  it  is  evident 
that  they  did,  in  the  light  of  recent  work  with  rabbits,  transmit 
the  disease  to  this  animal. 

The  first  Federal  participation  in  the  study  of  Rocky 
Mountain  spotted  fever  began  in  1903,  when  Passed  Assistant 
Surgeon  John  F.  Anderson,  of  the  Public  Health  and  Marine 
Hospital  Service,  was  detailed  by  Surgeon-General  Wyman 
to  make  investigations  in  Montana.  Anderson^  confirmed 
the  finding  of  Piroplasmata  in  the  blood  of  patients,  and 
supported  the  tick  transmission  theory  of  Wilson  and  Chown- 
ing.  He  noted  the  occurrence  of  the  disease  in  Oregon  in 
addition  to  the  other  states  previously  mentioned,  —  Montana, 
Idaho,  Nevada  and  Wyoming.  The  title  of  his  report  — 
"Spotted  Fever  (Tick  Fever)  of  the  Rocky  Mountains  —  a 
New  Disease  "  —  marks  the  acceptance  of  the  present  nomen- 
clature; Wilson  and  Chowning  used  the  same  expression, 
"  spotted  fever  "  or  "  tick  fever  of  the  Rocky  Mountains, '^ 
it  being  clear  to  all  that  this  eruptive  fever  was  restricted  to 
and  peculiar  to  the  Rocky  Mountain  states. 

The  tick  transmission  theory  aroused  considerable  local 
opposition  in  Montana,  partly  from  an  honest  disbelief  on 
the  part  of  physicians  who  occasionally  failed  to  get  evidence 
of  tick  bites  from  their  cases,  and  chiefly  from  those  interested 
in  the  economic  development  of  the  infected  localities.  This 
impression  I  gained  from  my  visit  to  Montana  in  191 7,  while 
Ashburn^  in  1905,  speaking  of  the  tick  theory,  says:  "  Eco- 
nomically, I  think  it  is  safe  to  say  it  has  been  more  disas- 
trous to  the  infected  region  than  the  disease  itself.  Ticks 
are  so  common  it  is  nearly  impossible  for  a  man  working" 


ROCKY   MOUNTAIN    SPOTTED   FEVER.  g 

out  of  doors  to  avoid  their  bites,  while  at  the  same  time 
they,  if  causing  the  disease,  constitute  a  cause  so  tangible  and 
real  that  the  dissemination  of  this  hypothesis  excited  a  fear 
closely  akin  to  terror.  Land  values  were  affected,  probably 
a  majority  of  the  people  on  the  west  bank  of  the  Bitter  Root 
River  desiring  to  sell  and  nobody  willing  to  buy.  Sawmills 
have  been  unable  to  procure  a  sufficiency  of  hands,  and  some 
families  have  sacrificed  their  property  in  order  to  get  away 
as  soon  as  possible.  People  who  formerly  frequented  that 
region  for  business  or  pleasure  could  in  most  instances  not 
now  be  induced  to  go  there,  except  on  most  urgent  business, 
during  the  tick  season." 

In  the  spring  of  1904,  Ch.  Wardwell  Stiles,  Chief  of  Division 
of  Zoology,  Hygienic  Laboratory,  United  States  Public  Health 
and  Marine  Hospital  Service,  was  detailed  by  Surgeon- 
General  Wyman  to  study  the  disease  "  from  a  zoological 
point  of  view."  The  special  purpose  of  his  detail  was  to 
"  trace  the  life  cycle  of  the  parasite  ('Piroplasma  hominis  ') 
which  has  been  described  as  the  cause  of  the  disease,  to 
study  the  tick  which  was  supposed  to  transmit  it,  and  to 
trace  the  disease  in  the  burrowing  squirrel  in  which  it  was 
thought  to  originate."  The  report  of  Stiles^^  contained  the 
most  complete  summary  of  knowledge  of  the  disease  that  had 
been  written.  His  refutations  of  all  of  Wilson's  and  Chown- 
ing's  conclusions  were  so  emphatic  that  they  savored  of  scorn. 
In  the  first  place,  he,  aided  by  Captain  Ashburn,  could  not 
demonstrate  the  Piroplasma  in  blood  preparations  made  by 
them  from  typical  cases  or  in  slides  sent  by  Wilson  and 
Chowning.  Chowning,  in  person,  was  unable  to  demonstrate 
the  parasites  to  Stiles  in  the  blood  of  a  typical  case.  In 
the  second  place.  Stiles  could  not  find  the  parasites  in  the 
blood  of  inoculated  rabbits  and  failed  to  transmit  the  disease 
to  rabbits  in  three  tests  from  three  different  typical  cases. 
Maintaining  as  he  did  that  the  tick  theory  was  a  secondary 
hypothesis  "  based  upon  the  idea  that  '  spotted  fever  '  is 
caused  by  a  protozoan,"  Stiles  may  have  been  justifiably 
prejudiced  by  his  failure  to  find  the  protozoan  and  made 
hazardous  use  of  analogy  in   disposing  of  the   tick  theory- 


10  WOLBACH. 

The  climatological  observations  made  by  him  are  interesting 
in  the  Hght  of  our  present  knowledge  of  the  habits  of  the 
tick  {Dermacentor  venustus).  Stiles  noted  that  the  incidence 
of  cases  was  highest  during  the  first  warm  days  of  spring, 
and  decreased  later  when  the  snow  had  melted.  The  retire- 
ment of  ticks  during  the  hot  days  of  July  apparently  escaped 
Stiles's  notice,  for  he  concluded  that  "  such  as  the  data  are, 
they  tend  to  support  rather  than  to  negative  the  popular  idea 
that  the  melting  of  snow  has  some  direct  or  indirect  connec- 
tion with  the  development  of  cases;  or  at  least  they  tend  to 
show  that  conditions  which  favor  the  melting  of  snow  also 
favor  the  appearance  of  cases  of  spotted  fever." 

Captain  Ashburn  in  1905  stated  with  force  his  belief  in 
the  disproof  of  the  tick  transmission  theory.  While  Stiles 
was  justified  in  not  accepting  as  proved  Wilson's  and  Chown- 
ing's  deductions  in  regard  to  tick  transmission,  and  advanced 
equally  logical  contrary  evidence,  subsequent  research  has 
proved  the  correctness  of  the  tick  theory,  the  susceptibility 
of  rabbits  and  the  importance  of  the  ground  squirrel  as  a 
host  of  the  virus  of  spotted  fever. 

Properly  organized  laboratory  investigation  of  Rocky 
Mountain  fever  began  in  the  spring  of  1906,  when  H.  T. 
Ricketts,  of  the  University  of  Chicago,  went  to  Montana. 
At  the  same  time  Passed  Assistant  Surgeon  W.  V.  King,  of 
the  Public  Health  and  Marine  Hospital  Service,  was  detailed 
to  investigate  the  disease  in  Nevada,  and  these  two  brilliant 
workers  cooperated  for  a  time  along  lines  of  research  directed 
by  Ricketts.  Ricketts  speedily  announced  the  transmission, 
by  inoculation  of  blood  from  human  cases,  of  the  disease  to 
monkeys  and  guinea-pigs  with  the  production  of  characteristic 
symptoms  and  lesions  and  fatal  effect. 

In  July  of  the  same  year  King  ^^  and  Ricketts  ^^  independ- 
ently transmitted  the  disease  to  guinea-pigs  by  means  of  the 
tick  {D.  venustus).  Thus  in  a  few  months  the  methods  of 
investigation  of  this  disease  were  blocked  out.  In  the  in- 
vestigation of  the  disease  for  several  years  following  Ricketts 
remained  preeminent  and  pursued  his  work  with  brilliancy 
and  keen  foresight. 


ROCKY    MOUNTAIN    SPOTTED    FEVER.  II 

A  period  also  followed  of  work  done  by  the  United  States 
Public  Health  Service  in  the  study  of  the  biology  of  the  tick 
and  of  methods  of  tick  control  as  leading  to  the  most 
direct  means  of  prevention  of  the  disease.  Of  the  workers 
engaged,  King,  McClintic,  Rucker  and  Fricks,  several  ex- 
hibited considerable  heroism  in  exposing  themselves  to  the 
disease,  and  McClintic  contracted  the  disease  in  the  summer 
of  1912,  while  at  work  in  the  Bitter  Root  Valley,  and  died. 
During  this  time  the  state  of  Montana  supported  in  part 
the  work  of  Ricketts,  and  under  the  leadership  of  Professor 
R.  A.  Cooley  conducted  valuable  investigations  in  part  in 
cooperation  with  the  Federal  Bureau  of  Entomology,  upon 
the  problems  of  tick  control. 

To  return  to  the  work  of  Ricketts  and  his  assistants  (Con- 
tributions to  Medical  Science,  by  Howard  Taylor  Ricketts. 
Univ.  of  Chicago  Press,  191 1)  between  1906  and  19 19,  we 
have  to  record  the  establishment  of  most  of  the  facts  now 
known  about  the  transmission  of  the  disease.  The  transmis- 
sion by  ticks,  the  demonstration  of  infective  ticks  in  nature, 
the  hereditary  passage  of  the  virus  through  generations  of 
ticks,  and  important  facts  regarding  immunity,  were  the 
product  of  his  work.  He  also  saw  the  microorganism  which 
is  now  shown  to  be  the  cause  of  the  disease,  but  unfortu- 
nately confused  it  with  bacteria  which  may  be  present  in 
non-infective  ticks. 

Remarkable  transmission  experiments  with  ticks  on  man 
were  made  in  1905  by  L.  P.  McCalla,^"  of  Boise,  Ida.,  but 
were  not  published  until  1908.  McCalla  removed  a  tick 
from  a  spotted-fever  patient,  and  with  consent  of  the  subjects 
of  the  experiments,  allowed  it  to  feed  for  forty-eight  hours 
upon  the  arm  of  a  man  and  immediately  after  removal  upon 
the  leg  of  a  woman,  where  it  remained  attached  over  ten 
hours  but  under  twenty-four  hours.  In  the  case  of  the  man 
there  was  an  incubation  period  of  nine  days,  when  a  typical 
case  of  spotted  fever  of  "  medium  severity  "  ensued,  with 
the  fever  lasting  "  about  eight  or  nine  days."  The  incubation 
period  in  the  woman  was  three  days.  The  fever,  rising  to 
101°  F.,  lasted  four  or  five  days  and  was  accompanied  by  a 


12 


WOLBACH. 


rash,  and  the  case  was  regarded  as  a  typical  "  mild  case." 
These  experiments,  antedating  the  transmission  experiments 
of  Ricketts  and  King,  are  the  only  recorded  instances  of  tick 
transmission  from  man  to  man. 

III.      DISTRIBUTION,  INCIDENCE  AND  MORTALITY. 

The  distribution  of  Rocky  Mountain  spotted  fever  is  that 
of  its  carrier,  the  wood  tick  Dermacentor  venustus,  although 
as  yet  no  case  has  been  reported  from  New  Mexico.     (Maps 


Map  I. 

Map  showing  the  distribution  of  the  Rocky  Mountain  spotted  fever 
tick  {Dermacentor  venustus).  The  degree  of  shading  indicates  the  relative 
abundance  of  the  tick  in  different  sections. 

Reproduced  from  Hunter  and  Bishopp.  United  States  Department  of  Agriculture^ 
Bureau  of  Entomology,  Bulletin  No.  105. 


ROCKY    MOUNTAIN    SPOTTED    FEVER. 


13 


Map  of  the  >ioi]NTAiNANDR\ciFic  States 

SHOWING  DISTRIBUTION  OF 

Rocky  Mountain  Spotted  Fever. 

W.TTZD  STATES  PUBLIC  HEALTH  SEBVICE 


The  dots  indicats  areas  of  infectiou  reported  previous  to  1915. 
Map  2. 

Reproduced  from  United  States  Public  Health  Reports,  xxx,  3,  1915. 


I  and  2.)  The  states  in  which  cases  have  unquestionably 
originated  are  Idaho,  Montana,  Nevada,  Oregon,  Utah, 
Wyoming,  California,  Colorado  and  Washington.  It  has  been 
asserted  that  the  disease  occurs  in  Alaska,  but  I  can  find 
no  proof  of  this.  Two  cases  were  reported  from  South 
Dakota  in  1915  (U.  S.  Public  Health  Reports). 

It  is   not   possible   in   general    to   determine   whether   the 
disease  is  spreading  over  wider  territories  from  year  to  year, 


14  WOLBACH. 

as  in  some  states  the  disease  is  not  reportable  and  no  wholly 
reliable  records  are  obtainable  from  any  source  from  any  state. 
Anderson/  in  1903,  records  cases  from  Montana,  Idaho, 
Nevada,  Wyoming  and  Oregon.  Stiles  ^^  in  1905  adds  Utah 
and  possibly  Alaska.  In  191 1  cases  were  reported  from 
California  in  the  Public  Health  Reports,  but  Kelly^^  has 
shown  that  the  disease  was  recognized  there  as  early  as  1903. 
Washington  appeared  as  a  source  of  spotted-fever  cases  in 
the  Public  Health  Reports  for  1914,  and  Colorado  in  1915. 
This  sequence  probably  has  no  significance,  as  the  sparsely 
settled  conditions  of  these  states  and  the  remoteness  of  the 
infected  regions  from  large  towns  would  tend  to  prevent  the 
reporting  of  such  few  cases  as  may  have  occurred  in  earlier 
years.  However,  in  Montana,  in  the  spring  of  1915,  the 
disease  appeared  suddenly  in  several  counties  in  the  eastern 
part  of  the  state,  where  its  presence  certainly  would  have 
been  known  had  it  existed  prior  to  that  time.  The  mortality 
in  eastern  Montana  is  much  lower  than  in  the  Bitter  Root 
Valley,  but  higher  than  in  Idaho.  Cooley's^^  conclusion 
that  the  disease  is  spreading  in  Montana  seems  warranted 
and  it  will  be  interesting  to  follow  further  developments  in 
this  and  other  infected  states. 

The  distribution  of  cases  in  the  various  states  is  character- 
istically restricted  to  certain  localities.  This  is  shown  strik- 
ingly by  the  Maps  3  and  4,  taken  from  the  Public  Health 
Reports  for  January  15,  191 5.  Idaho  furnishes  the  best 
example,  where  the  grouping  of  cases  in  certain  counties 
in  the  Snake  River  Valley  clearly  indicates  the  presence  of 
definite  foci  of  infection.  In  Montana  prior  to  1915  the 
disease  was  practically  restricted  to  the  west  side  of  the 
Bitter  Root  Valley,  and  although  it  has  since  appeared  in 
eastern  Montana,  the  east  slope  of  the  Bitter  Root  Valley 
remains  free  of  the  infection.  Some  of  the  factors  probably 
responsible  for  this  peculiarly  focal  distribution  of  the  virus 
in  nature  will  be  discussed  in  another  portion  of  this  paper. 
One  thing  seems  certain,  which  is  that  the  reservoir  of  the 
virus  is  some  animal  other  than  man. 


ROCKY   MOUNTAIN    SPOTTED    FEVER. 


15 


Map  OF  WvoMiNG. 
Rocky  Mountain  Spotted  Eever  Cases  upto  I9 1 5. 


A3    COLLECTED'"""  LOCAL  PHYSICIANS. 


I   iiaNIFICi   LOCATION  Of  C/t3£S. 


U5. Public  Health  Service. 


Map  3. 
Map    showing    distribution    of    Rocky    Mountain    spotted    fever    cases    in 

Wyoming. 

Reproduced  from  United  States  Public  Health  Reports,  xxx,  3,  1915. 


16 


WOLIJACH. 


Map  OF  Idaho -Rocky  Mountain  Spotted  Fever-  Year  191^. 

C»SE5  COLLECTED  BY  5TAT£  HEALTH  OmCER. 

DE/ITHS 

COUNT!  es  Cases 

ADA (n£ap>  BoiseS.   CountyS,) lb      1 

/ADAM5 {Council      I.   CountyI.) 3 

Qf\^Vi<dLV.-(50DA5PlilNGS  45.    PocflTELLO  /.) 54 

XPOMNEY  6.    S/t/vcftorr'f.  _>  ^  ^ 

Blaine c/ill  in  the  coc/ajty) 

B0I5E (fiosEBERf^y  7.      County  JO) // 

Bonneville- (^^////£^5  east  of  /oaho  Fails')  —  2 

C/\NYON (^ti EAR  Payette) lo  f 

Cassia {Burley^.  Oahley  Z.  County^ J4 

Elmore \ne/ir  MouNrfiiNHOME  ZS.  County'^'J)- T]  4 

SHOSHONE'm^ Gooding (Allinthe  county) 41  1 

■-%J;,KooT£NAi--('/?r  Poselahe) • 1  ? 

CLEARWATER    N:>i,^^  Latah ■■(/9rG£A^£5f£) 2 

iMlNIOOKA  ■■■('/v   THE  county) 2 

Lincoln (All  in  the  county) 4%      L 

i^r  OWYH EE •  •  -•  {NEfin  THE  COUNTY  line) Z 

.Washington ■•fC/?/va,^/z>Gf  Z4-^ 

KMlDVALE  /Z.\ 

\M£I'5EF>.  10) 

^%b    15 

•   5iCN/Fics  Loc/<rioN  Of  CnsEs. 


O  V^  Y  H  E  E 


UH-m  LO^Ft. 


U.S.  Public  He/>lth  Service 

Map  4. 

Map  showing  distribution  of  Rocky  Mountain  spotted  fever  cases  in 
Idaho  in  1914. 

Reproduced  from  United  States  Public  Health  Reports,  xxx,  3,  1915. 


ROCKY   MOUNTAIN    SPOTTED    FEVER.  1 7 

Wilson  and  Chowning,®^  in  1903,  had  obtained  histories 
of  one  hundred  and  twenty-six  cases  which  occurred  in  Mon- 
tana since  1885,  with  eighty-seven  deaths,  a  mortahty  of 
about  sixty-nine  per  cent,  including  all  ages  and  both  sexes- 
Their  table  is  worth  reprinting  here. 


Died. 

Males. 

Recov- 
ered.     Total. 

Died. 

Females. 

Recov- 
ered. 

Total. 

Total 
Both 
Sexes. 

Under  five  years     .    .    . 

4 

4 

8 

5 

0 

5 

13 

Five  to  ten  years    .    .    . 

5 

I 

6 

4 

3 

7 

13 

Ten  to  twenty  years 

5 

3 

8 

5 

6 

II 

19 

Twenty  to  thirty  years 

•      13 

4 

17 

3 

4 

7 

24 

Thirty  to  forty  years     . 

■     19 

5 

24 

7 

4 

II 

35 

Forty  to  fifty  years    .    . 

6 

2 

8 

I 

I 

2 

10 

Fifty  to  sixty  years    .    . 

2 

I 

3 

I 

I 

2 

5 

Sixty  to  eighty  years.    . 

4 

0 

4 

2 

0 

2 

6 

Age  not  stated    .... 

I 

0 

I 

0 

0 

0 

I 

Total 59         20         79         28         19         47       126 

The  age  incidence  in  this  table  is  probably  to  be  explained 
on  other  grounds  than  that  of  susceptibility.  In  the  first 
place,  in  all  newly  settled  districts  the  young  outnumber  the 
old,  and  again,  as  the  disease  is  contracted  out  of  doors, 
occupations  calling  for  exposure  necessarily  call  for  the  young 
and  vigorous.  Stiles®^  collected  eleven  cases  in  the  Bitter 
Root  Valley  in  1904,  with  nine  deaths.  Maxey,^*  in  1908, 
estimated  the  number  of  cases  occurring  annually  in  Idaho 
as  over  three  hundred  and  seventy-five.  In  1907  there  were 
three  hundred  and  sixty-three  cases  reported  to  the  Idaho 
State  Board  of  Health  from  about  one  half  of  the  physicians 
of  the  state  who  responded  to  the  inquiry.  The  mortality 
was  estimated  as  4.86  per  cent;  in  certain  localities,  howeverj 
the  mortality  may  have  been  higher,  and  in  his  conclusions 
Maxey  states  that  the  mortahty  varies  from  4.8  to  1 1.4  per 
■cent.  These  figures  are,  upon  consideration  of  the  character 
of  the  data  offered,  obviously  mere  approximations.  The 
Idaho  disease  is  stated  to  be  rarely  fatal  in  children  and 
adults,  and  quite  fatal  in  the  aged. 


1 8  WOLBACH. 

The  following  table  of  cases  in  the  Bitter  Root  Valley, 
from  1885  to  191 1  inclusive,  representing  data  collected  by 
Wilson  and  Chowning,  Anderson,  Stiles  and  McClintic,  was 
compiled  by  Assistant  Surgeon-General  Rucker.^^ 

United  States  Public  Health  Reports,  xxvii.  No.  36,  1912. 


Case  Fatality  Rate 

Year. 

Cases. 

Deaths. 

Per  Cent. 

1885 

I 

I 

ICO 

1886 

I  ■ 

I 

100 

1887 

0 

0 

0 

1888 

3 

I 

33-3 

1889 

3 

3 

100 

1890 

I 

I 

100 

1891 

6 

4 

66.6 

1892 

3 

I 

33-3 

1893 

4 

2 

50 

1894 

0 

0 

0 

1895 

3 

3 

100 

1896 

6 

6 

100 

1897 

6 

5 

83-3 

1898 

3 

2 

66.6 

1899 

23 

14 

60.8 

1900 

12 

9 

75 

1901 

14 

10 

71.4 

igo2 

21 

15 

71.4 

1903 

14 

9 

64.2 

1904 

II 

9 

81.8 

1905* 

1906* 

1907 

1908 

12 

5 

41.6 

1909 

28 

13 

46.4 

1910 

19 

14 

73-6 

1911 

16 

6 

37-5 

1912 

I 

I 

100 

Date  not  known 

4 

2 

50 

*  The  Third  Biennial  Report  of  the  Montana  State  Board  of  Health  gives 
ten  deaths  between  June  30,  1905,  and  June  30,  1906.  No  data  can  be  found 
covering  the  spring  of  1905  and  for  the  year  of  1907. 


ROCKY   MOUNTAIN    SPOTTED    FEVER. 


19 


The  following  data  (R.  A.  Cooley)  are  available  from 
Montana^^  (Montana  State  Board  of  Entomology,  Third 
Biennial  Report). 

Cases  in  the  Bitter  Root   Valley. 


Year. 

Ravalli 
County. 

Missoula 
County. 

Total 

I913 

0 

0 

II 

I914 

6 

4 

10 

I915 

3 

5 

8 

1916 

5 

I 

6 

I917 

5 

I 

6 

I918 

2 

I 

3 

Cases 

in  other  localities  in  Montana. 

Eastern  Counties. 

1915.      1916. 

917. 

Custer  .... 

8 

Dawson    .    .    . 

6 

4 

2 

Rosebud  .    .    . 

5 

Big:  Horn      .    . 

I 
2 

Fallon  .... 

Musselshell 

2 

Yellowstone     . 

3 

Fergus      .    .    . 

3 

Phillips     .    .    . 

Stillwater     .    . 

cases. 

2 

Scattering 

Carbon     .    .    . 

3 
2 
I* 

I 

Gallatin    .    .    . 

Cascade    .    .    . 

I9I8. 


Madison 


Total 28         12 

*  This  case  originated  in  Idaho. 


15 


The  mortality  of  these  cases  is  not  given;  however,  in  the 
Public  Health  Reports  compiled  by  Pricks, ^^'^^  we  find  for 
Montana  the  following  statistics:  1917,  twenty-five  cases, 
no  deaths  recorded;  1916,  nineteen  cases  with  six  deaths; 
1915,  thirty-eight  cases,  no  deaths  recorded;  1914,  ten  cases, 
no  deaths  recorded;  1913,  eight  cases  with  seven  deaths; 
1912,  twelve  cases  with  nine  deaths;  1911,  seventeen  cases 
with  six  deaths.  The  Federal  figures  are  obviously  less  accu- 
rate than  those  of  the  state,  as  frequently  I  have  been  able  to 
ascertain  the  double  reporting  of  a  single  case.     According  to 


20  ■  WOLBACH, 

Michie  and  Parsons^^  there  were  in  1912  eight  cases  in  Mon- 
tana, with  seven  deaths.  Of  the  twenty-two  cases  in  eastern 
Montana  in  191 5,  there  were  two  deaths  (Cooley^^).  Of  the 
six  cases  in   the   Bitter  Root  Valley  in  1917,  five  died. 

The  following  table  of  cases  includes  all  those  reported  in 
the  Public  Health  Reports  since  191 1,  when  the  first  records 
of  Rocky  Mountain  spotted  fever  appear.  The  mortality 
statistics  are  very  irregularly  and  probably  inaccurately 
stated,  and  the  reason  is  probably  the  desire  of  each  community 
to  conceal  the  fatalities.  This  intention  becomes  obvious 
to  any  one  upon  residence  for  a  time  in  such  a  region.  The 
Public  Health  Reports  data  have  been  verified,  and  in  several 
instances  corrected  by  consultation  of  the  State  Board  of 
Health  Reports  of  Nevada,  Washington,  Montana,  Oregon, 
Idaho  and  Utah. 

The  California  statistics  for  191 1  to  1915,  inclusively,  are 
taken  from  the  report  of  F.  L.  Kelly ,^^  to  whom  I  am  also 
indebted  for  the  191 7  and  191 8  figures  (personal  communi- 
cation). 

From  Michie  and  Parsons^^  we  learn  that  there  were  in 
Nevada  twenty-one  cases  between  191 1  and  1914  inclusive, 
without  fatality. 

If  we  take  the  years  1916  and  1915,  for  which  we  have  the 
most  complete  returns,  we  find  a  total  of  295  cases  for  19 16 
and  563  cases  for  191 5.  These  figures  undoubtedly  are 
probably  far  below  the  true  number.  Hunter  and  Bishopp^^ 
regard  750  cases  a  year  with  seventy-five  deaths  as  a  con- 
servative estimate. 

The  mortality  rate  is  impossible  to  determine.  In  the 
Bitter  Root  Valley  the  percentage  is  probably  above  seventy, 
as  estimated  by  Wilson  and  Chowning.^^  Estimated  for  all 
other  states  in  the  years  191 6  and  191 5,  where  deaths  have 
been  recorded,  it  is,  for  1916,  12.93  per  cent  and  for  1915, 
7.15  per  cent.  The  discrepancies  between  these  figures  illus- 
trate, the  absurdity  of  attempting  to  calculate  the  mortality 
from  the  published  data.  It  is  probably  safe  to  say  that 
the  mortality  outside  of  the  Bitter  Root  Valley  averages 
somewhere  between  7.15  and  13.0  per  cent. 


ROCKY    MOUNTAIN    SPOTTED    FEVER. 


21 


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22  WOLBACH. 

It  is  impossible  to  dismiss  the  subject  of  incidence  and 
mortality  without  the  comment  that  the  Federal  Public 
Health  Reports  records  of  Rocky  Mountain  spotted  fever 
are  valueless  and  that,  as  given  in  recent  years,  can  fulfill  no 
purpose  whatsoever. 

There  are  also  marked  discrepancies  between  the  figures 
for  certain  years  as  published  by  Fricks,^^-^^  and  those  by 
Kelly^^  for  California,  and  those  for  Montana  in  the  Third 
Biennial  Report  of  the  State  Board  of  Entomology.  In  the 
face  of  such  differences,  I  have  chosen  the  latest  report  on 
the  cases  for  the  years  in  question,  such  figures  being  in 
most  instances  the  highest  and  presumably,  therefore,  the 
most  complete. 

IV.      CLINICAL  DESCRIPTION. 

1.  Definition.  —  In  1899  Maxey''^  defined  "  Rocky  Moun- 
tain spotted  fever  "  as  "  an  acute  endemic,  non-contagious 
but  probably  infectious  febrile  disease,  characterized  clinically 
by  a  continuous,  moderately  high  fever,  severe  arthritic  and 
muscular  pains,  and  a  profuse  petechial  or  purpural  eruption 
in  the  skin,  appearing  first  on  the  ankles,  wrists  and  forehead, 
but  rapidly  spreading  to  all  parts  of  the  body." 

In  view  of  the  researches  here  presented,  the  following 
definition  becomes  more  appropriate:  An  acute  specific  in- 
fectious endangeitis,  chiefly  of  the  peripheral  blood  vessels, 
transmitted  by  a  tick,  Dermacentor  venustus,  and  characterized 
by  onset  with  chill,  continued  fever,  severe  pains  in  bones 
and  muscles,  headache  and  a  macular  eruption  becoming 
petechial,  which  appears  first  on  wrists,  ankles  and  back, 
then  over  the  whole  surface  of  the  body. 

2.  Seasonal  incidence.  —  The  disease  occurs  almost  wholly 
in  the  spring  months  corresponding  to  the  period  of  activity 
of  the  ticks.  The  first  cases  appear  usually  in  March  after 
the  melting  of  the  snow,  and  the  number  of  cases  increases 
as  the  number  of  active  adult  ticks  increases.  May  and 
June  are  the  months  of  greatest  incidence.     Few  cases  occur 


ROCKY   MOUNTAIN    SPOTTED    FEVER.  23 

during  July,  while  very  rarely  a  case  occurs  in  August,  Sep- 
tember and  October.  These  late  cases  are  probably  con- 
tracted at  high  altitudes,  from  ticks  which  have  emerged  late 
from  hibernation  following  melting  of  the  snow. 

3.  Incubation.  —  In  McCalla's^^  experiment  upon  two 
humans,  the  incubation  periods  were  three  and  nine  days. 
Stiles^^  records  four  cases  where  the  onset  of  the  disease 
occurred  once  on  the  fifth  day,  twice  on  the  sixth  day  and 
once  on  the  seventh  day  after  the  discovery  of  the  tick. 
In  many  guinea-pig  experiments  I  have  found  the  shortest 
incubation  period  to  be  between  three  and  four  days  after 
attachment  of  the  tick,  the  longest  period  seven,  the  usual 
period  from  four  to  five  days.  As  Ricketts  and  Moore^^ 
showed  that  the  average  duration  of  feeding  necessary  for  a 
tick  to  infect  is  about  ten  hours  (the  shortest  period  being 
about  two  hours)  and  as  the  guinea-pig  is  probably  more 
susceptible  than  man,  incubation  periods  in  man  reported 
as  less  than  three  days  are  probably  incorrect. 

Wilson  and  Chowning^^  give  two  to  eight  days  (five  cases 
of  two  days,  one  each  of  three,  five,  six,  seven  and  eight  days, 
two  cases  determined  as  between  the  second  and  fifth  days). 
Anderson,^  three  to  ten  days;  Ashburn,^  two  to  eight  days; 
Stewart  and  Smith, ^^  five  to  seven  days;  Rucker,^^  three  to 
ten  days;  Fricks,^^  two  to  twelve  days,  usually  four  to  seven 
days;   and  Michie  and  Parsons, ^^  three  to  eight  days. 

Three  to  twelve  days  are  probably  the  limits  of  the  in- 
cubation period .  It  is  certain  that  most  cases  develop  between 
the  fourth  and  eighth  days  after  discovery  of  the  feeding  tick. 

4.  Symptoms  and  course.  Onset.  —  The  onset  of  the 
disease  is  usually  accompanied  by  a  chill,  though  there  may 
be  a  few  days  of  malaise  with  loss  of  appetite  accompanied 
by  chilly  sensations  before  a  frank  chill  occurs.  This  latter 
mode  of  onset  is  more  common  in  Idaho  than  in  Montana, 
and  must  be  in  some  way  related  to  the  less  fatal  course  of 
the  disease  in  Idaho.  There  is  nothing  peculiar  in  the  behavior 
of  the  lesion  caused  by  the  bite  of  an  infected  tick  as  compared 


24 


WOLBACH. 


with  that  of  a  non-infected  tick.  From  the  start  there  are 
severe  general  pains  referred  to  the  bones  and  muscles,  back 
and  joints.  Pains  in  the  calf  muscle  and  large  joints  and 
lumbar  region  of  the  back  are  the  most  prominent.  Headache 
is  common  and  is  usually  severe.  The  face  is  flushed,  the 
conjunctivae  injected,  the  tongue  white  and  coated,  with  moist 
red  tip  and  edges  and  there  is  constipation.  The  patient  is 
usually  ill  enough  to  take  to  his  bed  on  the  second  day  of 
symptoms.  There  may  be  epistaxis,  and  there  usually  is 
photophobia.  A  very  common  symptom  is  a  short  cough 
without  sputum,  evidently  due  to  bronchial  irritation. 

5.  Temperature.  — The  temperature  before  the  initial  chill 
is  not  high;    there  is  a  slight  evening  rise  only.     After  the 


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Charts  of  temperature,  pulse  and  respiration  from  a  case  of 
Rocky  Mountain  spotted  fever  with  recovery.  Male,  Albert  M.^ 
age  16.     From  Michie  and  Parsons. 


ROCKY   MOUNTAIN    SPOTTED    FEVER. 


25 


chill  the  temperature  rises  fairly  rapidly  and  reaches  102°  F. 
to  104°  F.  in  the  second  day,  and  continues  to  rise  gradually 
to  a  maximum  of  104°  F.  to  105°  F.  during  the  second  week. 
In  severe  cases,  in  the  Bitter  Root  Valley,  the  temperature 
reaches  106°  F.  to  107°  F.  and  may  remain  this  high  until 
death.  The  maximum  temperature  is  reached  more  quickly 
in  the  virulent  Montana  cases  than  in  the  Idaho  type  of  the 
disease. 


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Charts  of  temperature,  pulse  and  respiration  illustrating  a  fatal  case  of 
Rocky  Mountain  spotted  fever.  Case  CXX.,  male,  E.  M.,  age  28.  Re- 
produced from  data  published  by  Anderson. 

The  maximum  temperature  persists  during  the  second  week 
of  the  disease,  with  slight  morning  drops.  In  cases  which 
recover,  the  temperature  begins  to  lower  at  about  the  end 
of  the  second  week  and  falls  by  lysis  so  that  normal  tempera- 
ture is  reached  on  about  the  end  of  the  third  week.     The 


26  WOLBACH. 

temperature  may  go  to  98°  F.  or  below  for  a  few  days  after 
recovery.  In  fatal  cases  the  temperature  may  drop  to  normal 
or  subnormal  and  then  rise  eighteen  to  twenty-four  hours 
before  death.  Death  in  the  severe  cases  such  as  occur  in 
the  Bitter  Root  Valley  usually  takes  place  between  the  sixth 
and  twelfth  days  of  the  disease,  or  from  three  to  seven  days 
after  the  eruption  appears.  Thus,  in  ninety-six  fatal  cases 
where  data  are  available,  seventy-nine  died  between  the  sixth 
and  twelfth  days  of  the  disease  (Stiles^^).  Fifty-three  of 
seventy-two  fatal  cases  died  between  the  third  and  seventh 
days  of  the  rash. 

6.  Pulse  and  respiration.- — The  pulse  at  first  is  full  and 
strong,  but  gradually  loses  volume  and  strength  and  increases 
in  rapidity  out  of  proportion  to  the  temperature.  The  same 
applies  to  the  respirations,  which  become  very  rapid  and 
shallow  in  severe  cases.  The  pulse  ranges  from  no  to  140 
and  may  reach  150  a  few  days  before  death.  A  pulse  of  120 
with  a  temperature  of  102°  F.  is  not  uncommon.  The  respira- 
tions usually  are  from  thirty  to  forty  a  minute  but  may  rise 
to  sixty  before  death.  A  rapid  increase  in  rate  of  pulse  and 
respiration  is  of  decidedly  bad  prognostic  significance. 

7.  Eruption. — The  rash  appears  usually  on  the  third, 
fourth  or  fifth  day  of  fever,  most  often  on  the  third  day. 
It  may  show  as  early  as  the  second  or  as  late  as  the  seventh 
day  of  temperature.  There  is  very  marked  uniformity  in 
the  statements  of  all  authors  in  respect  to  the  development 
and  characteristics  of  the  rash.  It  shows  first  on  the  wrists, 
ankles  and  back,  then  forehead,  arms,  legs  and  chest,  and 
lastly  upon  the  abdomen,  where  it  is  always  least  marked. 
It  takes  about  twenty-four  to  thirty-six  hours  for  the  efflores- 
cence of  the  rash,  though  later  than  this  the  palms  of  the  hands, 
soles  of  the  feet,  the  scalp  and  the  mucosa  of  the  cheeks, 
palate,  pharynx  and  fauces  may  become  sites  of  the  eruption. 
With  the  coming  of  the  rash  the  general  aches  and  pains 
ameliorate  but  the  temperature  is  not  appreciably  affected. 


ROCKY   MOUNTAIN    SPOTTED    FEVER.  2/ 

The  rash  consists  at  first  of  rose-colored  macules  not  ele- 
vated, in  size  from  less  than  one  to  four  or  five  millimeters 
in  diameter  and  disappearing  upon  pressure.  Rarely  the 
skin  is  tender  at  the  sites  of  the  spots.  The  spots  soon 
become  deep  red  or  purplish  and  increase  in  size,  often  be- 
coming confluent,  thus  giving  a  diffuse  marbled  appearance 
to  the  skin.  After  several  days'  duration  some  of  the  spots 
no  longer  disappear  upon  pressure  (sixth  to  tenth  day  of  the 
disease)  and  then  the  rash  becomes  distinctly  petechial  in 
character.  In  severe  cases  areas  of  cutaneous  and  sub- 
cutaneous hemorrhage  of  considerable  size  occur,  and  fre- 
quently the  skin  assumes  a  glazed  appearance  in  the  second 
week  of  the  disease.  A  peculiarly  dusky  reddish  or  bluish 
mottling' of  the  skin  of  the  thighs  may  occur,  and  is  due  to 
stasis  of  blood  in  the  subcutaneous  vessels. 

If  the  rash  does  not  become  confluent,  the  thickly  dis- 
tributed, discrete  red  or  reddish-brown  spots  give  an 
appearance  to  the  skin  which  several  Idaho  physicians  have 
compared  to  the  markings  of  a  turkey's  egg. 

Icterus  appears  in  the  second  week  of  the  disease,  but  is 
never  very  marked. 

The  rash  begins  to  disappear  with  the  subsidence  of  fever 
but  the  site  of  the  petechise  is  long  indicated  by  pigment 
spots.  In  severe  cases,  in  the  third  week,  necrosis  of  the 
skin  of  certain  dependent  parts  frequently  occurs.  As  will 
be  seen  from  the  pathology  of  the  disease,  this  necrosis  is 
secondary  to  occlusion  of  blood  vessels,  and  is  therefore 
necessarily  a  late  effect  and  accordingly  is  more  common  in 
Idaho  than  in  the  Bitter  Root  Valley.  The  skin  necrosis 
is  most  common  of  the  scrotum,  prepuce,  fingers,  toes  and 
lobes  of  the  ear.  Necrosis  also  may  affect  the  soft  palate 
(Stewart  and  Smith^^). 

Desquamation  follows  recovery,  and  extends  over  the  whole 
body,  but  is  slight  except  where  the  skin  lesions  were  most 
marked.  In  exceptional  cases  casts  over  sites  of  large  hemor- 
rhages from  the  palms  and  soles  may  be  formed  (Stewart  and 
Smith^2)_  Maxey^^  describes  on  the  palms  and  soles  the 
common  formation  of  discrete,  white  areas  of  dead  epidermis. 


28  WOLBACH. 

corresponding  to  areas  of  cuticular  hemorrhages,  which  on 
being  picked  off  leave  shallow  depressions  in  the  skin.  Le- 
sions indicating  the  former  sites  of  the  petechiae  may  persist 
for  weeks  and  months  and  become  demonstrable  after  chilling 
the  skin,  or  after  severe  exercise  or  a  hot  bath.  It  is  incorrect 
to  speak  of  this  as  a  persistence  of  the  rash  —  the  effect  is 
undoubtedly  due  to  cicatrices  and  local  obliteration  of  the 
capillaries  of  the  skin. 

8.  Nervous  symptoms.  —  Restlessness  and  insomnia  are 
very  common  throughout  the  disease,  and  are  among  its  most 
distressing  features.  Hyperesthesia  is  frequent  and  often 
very  severe,  the  slightest  touch,  movement  of  the  bed  or 
even  the  weight  of  the  bedclothes  may  cause  extreme  pain. 

Delirium  is  usual  in  severe  cases  during  the  height  of  the 
fever  and  coma  usually  precedes  death  by  a  few  hours  to  a 
day.  Convulsions  and  muscular  rigidity  and  opisthotonos 
are  very  rare  conditions  reported. 

9.  Gastro-intestinal  symptoms.  —  Constipation  is  present 
from  the  onset,  and  persists  throughout  the  disease.  Vomiting 
may  occur  during  the  onset  and  again  late,  preceding  a  fatal 
termination.  As  a  rule,  the  appetite  and  digestion  are 
affected  as  in  any  febrile  disease,  and  both  may  be  good 
during  the  first  week. 

Sordes  and  coated  tongue  occur  as  in  other  febrile  diseases. 

10.  The  urine.  —  The  urine  is  reduced  in  amount  to  about 
one  half  normal.  It  is  high  colored  and  may  contain  small 
amounts  of  albumin.  Casts  of  various  sorts  are  often  present, 
granular,  and  occasionally  blood  casts  are  found. 

In  two  cases  in  which  I  examined  the  urine  no  albumin 
was  present.  Maxey^  states  he  never  found  albumin  in  his 
large  experience. 

In  general,  the  urine  shows  the  characteristics  common  to 
severe  fevers  without  especial  renal  involvement. 

11.  The  blood.  —  There  are  but  few  records  of  blood  counts 
in  the  literature,  and  no  complete  record  exists  of  any  one 


ROCKY    MOUNTAIN    SPOTTED    FEVER.  2() 

case.  This  is  due  naturally  to  the  difficult  conditions  sur- 
rounding the  cases  in  rural  and  often  remote  districts  and 
to  the  fact  that  most  cases  arrive  at  hospitals  late  in  the 
course  of  the  disease. 

A  few  facts,  however,  are  established.  There  is  only  a 
slight  leucocytosis  —  the  white  count  in  uncomplicated  cases 
does  not  go  above  12,000.  The  red  cells  decrease  in  number 
as  the  disease  progresses  and  may  fall  below  3,500,000  before 
death. 

There  is  a  striking  increase  in  large  mononuclear  leucocytes, 
apparently  exclusive  of  large  lymphocytes  and  so-called 
"  transitional  cells."  I  have  found  phagocytic  cells  in  the 
circulation  shortly  before  death.  The  eosinophiles  are  de- 
creased and   may  be  entirely  absent  in  some  preparations. 

Most  observers  report  the  blood  as  being  darker  and 
less  fluid  than  normal.  Michie  and  Parsons^^  state  that  the 
coagulation  time  is  increased. 

The  hemoglobin  becomes  slightly  reduced. 

As  the  number  of  blood  observations  is  so  small,  I  present 
the  data  as  published. 

Anderson^  gives  the  average  of  the  differential  white  cell 
counts  in  two  cases;  the  age,  sex  and  day  of  disease  are  not 
stated. 

Per  Cent. 

Polymorphonuclear  leucocytes 77-7 

Large  mononuclear  leucocytes      .' 11 -4 

Small  lymphocytes lO-O 

Eosinophiles 0.9 

He  also  gives  the  red  and  white  cell  counts  and  hemoglobin 
estimation  of  several  cases  included  in  the  chart  of  Wilson 
and  Chowning. 

Michie  and  Parsons^^  report  the  presence  of  myelocytes  and 
nucleated  red  cells  and  the  presence  of  leucocytes  in  severe 
cases  which  they  are  unable  to  classify.  They  regard  the 
"  Arneth  Index  "  as  a  reliable  guide  to  the  patient's  condition, 
and  present  the  following  table  of  blood  counts  from  two  cases. 


30 


WOLBACH. 


Group. 


A  sudden  increase  of  leucocytes  late  in  the  disease 

garded  by  them  as  a  serious  sign. 

Case   i.     Westerman.     Fatal.     Death  on  May  20,  1912. 

Arneth  count. 
Date. 

May  15,  1912  

May  16,  1912  

May  17,  1912  

May  18,  1912  

May  19,  1912  

May  20,  1912  


IS  re- 


I. 

II. 

III. 

Index. 

IV. 

V. 

7 

47 

33 

70 

12 

I 

7 

53 

33 

76.5 

6 

I 

5 

58 

35 

80.5 

2 

0 

9 

61 

22 

81 

8 

0 

6 

57 

34 

80 

2 

I 

5 

60 

31 

80.5 

2 

2 

May  15,  1912 
May  16,  1912 
May  17,  1912 


Leucocyte  count. 

11,800  May  18,  1912 3,000 

11,000  May  19,  1912  ....".  1,000 

6,000  May  20,  1912 28,000 


Differential  count. 


15.  16. 

Large  lymphocytes 6  3 

Small  lymphocytes 2  3 

Large  mononuclears 19  11 

Polymorphonuclear  neutrophiles,      65  75 

Transitionals 5  4 

Eosinophiles i  i 

Mast  cells o  i 

Unclassified      .........        i  2 

Myelocytes 2  o 

Nucleated  red  cells o  o 

*  Present. 

t  Leucocytes  were  extremely  scarce  on  May  19,  1912,  and  the  above  count 
is  based  on  forty  cells  after  one  hour's  search. 


Dates  — 
17. 

4 
I 

47 
II 
o 
o 
5 
5 
o 


May,  1912. 

18.  19. 

2t 
O 

15 

55 

16 

o 

o 

10 

2 

p* 


o 
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II 

68 

17 
o 
o 

2 

2 
p* 


4 
2 

25 

32 

18 

o 

o 

15 


Case  2. 
ninth  day. 


Male,  aged  24  years.     A  typical    fatal .  case,  death    on   the 


Differential  count. 


Large  lymphocytes 

Small  lymphocytes 

Large  mononuclears 

Polymorphonuclear  neutrophiles. 

Transitionals 

Eosinophiles 

Mast  cells 

Unclassified 

Myelocytes      

Nucleated  red  cells Present.  Present. 

Leucocyte  count:     May  7,  11,800;    May  8,  7,120;    May  9,  16,000. 


Eighth  Day. 
Per  Cent. 

Ninth  Day. 
Per  Cent. 

8 

2 

5 

4 

20 

II 

34 

45 

26 

19 

2 

0 

2 

2 

3 

8 

0 

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ROCKY    MOUNTAIN    SPOTTED    FEVER. 


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32  WOLBACH. 

To  these  counts,  I  have  the  following  of  my  own  to  add: 

Case  i.     Woman,  aged  26  years.     Died  on  the  ninth  day  of  the  disease. 

Sixth  Day  of  Seventh  Day  of 

Disease.  Disease. 

White  count 7, 300  7, 300 

Red  count 5,008,000 

Differential  count. 

Polymorphonuclear  leucocytes     .    .    .          81.2%  54-0% 

Large  lymphocytes 10.4%  26.5% 

Small  lymphocytes 3-9%  8.7% 

Large  mononuclear  leucocytes     .    .    .            4-4%  8.0% 

Eosinophiles 0.0%  2.2% 

Case  2.  Man,  aged  75  years.  Fifth  day  of  disease,  second  day  of  rash» 
one  day  before  death. 

Polymorphonuclear  leucocytes 28.6% 

Large  lymphocytes 23.8% 

Small  lymphocytes 35.8% 

Large  mononuclear  leucocytes ii-3% 

Eosinophiles 0.0% 

Blasts 1.0% 

Case  3.     Man,  aged  31  years.     Died  on  the  eighth  day  of  the  disease. 

Sixth  Day.  Seventh  Day. 

Polymorphonuclear  leucocytes     .    .    .          85.4%  87.0% 

Large  lymphocytes 6.2%  7-2% 

Small  lymphocytes 2.6%  3-5% 

Large  mononuclears 5-8%  2.6% 

Eosinophiles 0.0%  0.0% 

-Blasts Present.  Present. 

Case  4.     Man,  young  adult.     Died  on  ninth  day  of  disease. 
Blood  counts  on  third  day  of  disease. 

Red  cells      5,400,000 

White  cells 10,000 

Polymorphonuclear  leucocytes     ....  87% 

Hemoglobin 80% 

The  most  striking  feature  of  the  blood  picture  is  the  increase 
in  large  mononuclear  leucocytes.  In  Case  2,  cells  with 
inclusions  of  red  cells  and  lymphocytes  were  found  the  day 
before  death,  and  there  is  excellent  evidence  from  the  histo- 
logical study  of  all  my  cases  to  show  that  one  source  of  the 
large  mononuclear  leucocytes  in  the  circulation  in  these  cases 
is  from  the  vascular  endothelium.  In  all  cases  the  poly- 
morphonuclear leucocytes   frequently  contained  small   basic 


ROCKY   MOUNTAIN    SPOTTED    FEVER.  33 

•staining  bodies  (Dohles'  inclusions,  Miinch.  Med.  Wochen- 
schr.,  July  23,  1912)  common  in  scarlet  fever  and  some  other 
infections. 

12.  Complications.  —  Pneumonia  is  the  one  complication, 
and  it  is  not  frequent.  Broncho-pneumonia,  hypostatic  pneu- 
monia and  lobar  pneumonia  have  been  reported  in  a  few  cases. 

13.  Types  of  the  disease.  - —  It  is  possibly  justifiable  to  speak 
of  a  mild  and  a  severe  type  of  Rocky  Mountain  spotted  fever, 
in  view  of  the  great  difference  between  the  mortalities  of 
Idaho  and  Montana  cases.  However,  as  in  other  regions 
the  mortality  is  intermediate  between  that  of  Idaho  and 
Montana,  this  distinction  should  be  used  with  caution,  par- 
ticularly as  in  some  localities  in  Idaho  the  mortality  is  quite 
high.  In  all  other  respects  the  disease  in  Idaho  and  Montana 
IS  identical,  although  because  of  the  lesser  virulence  in  Idaho 
the  late  effects,  such  as  necrosis  of  the  skin,  are  more  often 
seen. 

No  solution  of  the  cause  of  the  consistent  difference  in 
inortality  of  cases  from  these  two  regions  has  been  found. 
Theoretical  considerations  point  to  a  solution  in  the  different 
types  of  mammalian  hosts  other  than  man,  and  opportunities 
for  rapid  mammalian  passage  of  the  virus. 

14.  Treatment.  —  There  is  no  specific  treatment.  The 
fever  should  be  treated  by  the  general  measures  employed 
in  other  continued  fevers.  Cold  bathing  should  be  employed 
to  reduce  temperature  and  to  allay  nervous  symptoms,  with 
observation  of  the  same  precautions  used  in  typhoid  and 
typhus  fevers.     Antipyretic  drugs  should  be  avoided. 

The  diet  should  be  nutritious,  easily  digestible  and  liberal, 
particularly  in  the  first  stages  of  the  disease,  in  order  to  keep 
up  the  strength  of  the  patient.  As  the  kidneys  and  alimentary 
tract  escape  lesions,  there  is  no  reason  against  a  liberal  diet 
until  the  time  when  nausea  occurs  as  a  result  of  the  general 
intoxication.  It  would  even  seem  advisable  to  force  the  diet 
;in  the  early  days  of  the  disease.     A  liberal  liquid  intake  is 


34  WOLBACH. 

indicated  also,  in  order  to  increase  the  output  of  urine.  The 
bowels  should  receive  attention  from  the  start  of  the  disease 
and  a  daily  movement  secured  by  aperients  or  enemata. 

The  modern  use  of  digitalis  in  pneumonia  might  well  be 
followed  in  anticipation  of  circulatory  changes  late  in  the 
disease.  A  few  doses  of  digitalis  at  the  onset  of  the  disease 
in  order  to  "  digitalize  "  the  heart  is  therefore  recommended, 
to  be  followed  by  further  administration  of  the  drug  when  the 
pulse  rate  becomes  over  rapid. 

Since  the  restlessness,  hyperesthesia  and  insomnia  un- 
doubtedly are  of  great  importance  in  the  production  of  ex- 
haustion, hypnotics  should  be  given  in  amount  sufficient  to 
insure  adequate  rest  for  the  patient.  Morphine  and  hyoscine 
may  be  recommended,  and  I  can  think  of  no  deleterious 
action  of  these  drugs  that  overweighs  the  importance  of 
their  action.  In  general,  the  therapeutic  measures  employed 
should  be  directed  towards  conserving  the  strength  of  the 
patient  and  allaying  discomfort,  thus  insuring  the  most 
favorable  circumstances  for  the  natural  forces  of  the  body 
against  the  infection. 

The  various  drugs  which  have  been  employed  without 
beneficial  action  are  quinine,  the  coal-tar  products,  calcium 
sulphide,  creosote,  various  forms  of  arsenic  including  atoxyl,, 
salvarsan  and  sodium  cacodylate  and  sodium  citrate  injections. 
Salvarsan  and  atoxyl  are  decidedly  deleterious  in  their  effect. 
The  efforts  of  Ricketts  and  his  associates,  Heinemann  and 
Moore, ^^  to  produce  an  immune  serum  in  horses  have  given 
indication  of  possible  success,  but  the  work  was  not  continued 
long  enough  to  demonstrate  the  value  of  such  a  serum.  The 
intravenous  administration  of  human  serum  or  blood  from  an 
individual  who  has  recovered  from  the  disease  one  or  two 
years  previously  is  theoretically  worth  trying  in  districts 
where  the  mortality  is  high.  To  be  effective  the  serum  or 
blood  should  be  given  early  in  the  disease  and  in  as  large 
amounts  as  possible.  In  two  cases.  Cases  i  and  3  of  my 
series,  blood  transfusions  were  tried,  but  in  both  instances 
late  in  the  disease,  and  without  beneficial  results. 


ROCKY   MOUNTAIN    SPOTTED    FEVER.  35 

V.      PREVIOUS  WORK  ON  THE  PATHOLOGY. 

The  number  of  post-mortem  examinations  recorded  is  small 
and  not  as  large  as  a  casual  inspection  of  the  literature  would 
suggest,  because  several  authors  have  each  reported  the  same 
cases. 

Wilson  and  Chowning"^  report  a  summary  based  upon 
eight  autopsies,  and  Anderson^  one  based  upon  seven  cases. 
Anderson's  cases  are  included  among  Wilson's  and  Chowning's 
cases,  and  presumably  most  of  them  represent  the  work  of 
the  latter  authors.  There  were  six  autopsies  by  Ricketts^^ 
(Carpenter  Lecture)  summarized  by  Le  Count, ^o  and  one  by 
Michie  and  Parsons.  Stiles^^  and  Ashburn^  each  report  post- 
mortem results  from  cases  in  the  series  of  Wilson  and  Chowning 
or  Anderson.  As  far  as  can  be  determined,  fifteen  autopsies 
have  been  made,  all  upon  Bitter  Root  Valley  cases. 

I.  Gross  pathology. — Wilson  and  Chowning,  and  Ander- 
son, noted  the  early  onset  of  intense  rigor  mortis.  The  only 
constant  distinctive  gross  lesions  are  those  of  the  skin  and 
enlargement  of  the  spleen.  The  musculature  of  the  body, 
peritoneal,  pleural  and  pericardial  cavities  are  normal.  The 
heart  may  show  minute  hemorrhages  into  the  epicardium, 
and  as  a  rule  the  right  side  of  the  heart  is  distended  with 
blood  — the  left  side  contracted.  The  lungs,  beyond  hypos- 
tasis and,  occasionally,  terminal  pneumonia,  are  normal. 

The  spleen  is  reported  as  markedly  enlarged  in  all  cases, 
and  may  weigh  from  two  to  four  times  the  normal.  Wilson 
and  Chowning,  and  Anderson,  report  the  spleen  as  soft, 
while  Michie  and  Parsons,  and  Ricketts,  emphasize  its  firm- 
ness. The  latter  specifically  states  that  it  has  "  none  of  the 
soft,  semi-gelatinous  appearance  of  the  typhoid  spleen  " ; 
which  is  in  accordance  with  my  own  observations. 

The  liver  has  consistently  been  recorded  as  large,  pale, 
injected,  and  often  as  fatty.  Wilson  and  Chowning,  and 
Anderson,  note  stasis  of  bile  in  the  ducts. 

The  gastrointestinal  tract  has  shown  no  lesions.  The 
pancreas,  according  to  Anderson,  is  enlarged.  The  kidneys 
also   are  said   to  be   enlarged,   injected  and  degenerated  or 


2,6  WOLBACH. 

fatty.  Ricketts  did  not  note  the  subcapsular  hemorrhages 
noted  by  the  other  authors.  The  bladder  and  uterus  show- 
no  lesions.  No  lesions  have  been  noted  in  the  aorta,  vena 
cava  and  large  arteries  and  veins  of  the  trunk  and  extremities. 
The  lymph  nodes,  according  to  Ricketts,  are  uniformly  en- 
larged. Anderson  states  they  are  not  enlarged.  In  two  of 
Ricketts'  cases  the  bone  marrow  was  red.  The  central 
nervous  system  has  shown  no  lesions  beyond  injection  of  the 
meningeal  vessels.  The  lesions  of  the  skin  found  after  death 
consist  of  hemorrhages  into  the  subcutaneous  tissues,  and 
gangrene,  the  latter  usually  of  the  scrotum  and  prepuce, 
rarely  of  the  faucial  pillars  and  soft  palate.  The  gross  pathol- 
ogy is  therefore  not  distinctive  except  for  the  skin  lesions. 
Otherwise  the  findings  have  been  essentially  those  of  any 
infectious  disease. 

2.  Microscopic  pathology.  —  Wilson  and  Chowning,^^  and 
Le  Count^''  only  have  given  accounts  of  the  pathologic  his- 
tology. The  former  present  a  very  superficial  account  and 
record  no  distinctive  lesion  of  the  disease.  They  do  note 
capillary  hemorrhages  in  the  skin  and  the  accumulation  of 
leucocytes  in  the  capillaries  of  the  skin  and  liver.  They  also 
noted  phagocytic  cells  containing  rpd  blood  cells  in  the  capil- 
laries of  the  skin,  lungs,  spleen,  liver  and  kidney  —  a  fair  por- 
tion of  their  description  is  concerned  with  the  presence  of 
"  infected  red  cells."  Their  summary  is  - —  "  The  changes  are 
those  which  can  be  ascribed  to  interference  with  capillary  cir- 
culation. The  extravasation  into  and  pigmentation  of  the  skin 
account  for  the  persistence  of  the  '  spots  '  for  long  periods 
after  the  recovery  of  the  patients.  There  is  acute  paren- 
chymatous degeneration  of  the  heart  muscle,  spleen,  liver  and 
kidney.     The  central  nerve  system  is  but  little  affected." 

Le  Count  summarized  the  study  of  tissues  from  six  monkeys, 
thirty-two  guinea-pigs  and  six  human  cases.  His  descrip- 
tions are  very  brief  and  give  the  impression  of  his  having  seen 
more  than  he  recorded.  He  noted  as  the  most  distinctive 
lesion,  occlusion  of  blood  vessels  and  the  resultant  necroses. 
"  In  sections  of  the  skin,  liver,  kidney,  spleen  and  adrenal 


ROCKY    MOUNTAIN    SPOTTED    FEVER.  37 

both  vascular  occlusion  and  the  necroses  resulting  from 
obstruction  were  present.  In  the  lung  and  heart  the  capil- 
laries and  small  veins  were  found  practically  occluded  with 
leucocytes,  but  there  were  no  serious  consequences  of  these 
conditions  with  exception  of  minute  hemorrhages  beneath 
the  endocardium."  Le  Count  attributed  the  necroses  of  the 
ears  and  scrotum  of  guinea-pigs  to  "  anaemia  from  plugging 
of  small  blood  vessels,"  but  he  does  not  describe  the  histology 
and  development  of  the  lesion  which  leads  to  thrombosis. 
Focal  lesions  in  liver  and  spleen  are  described  as  attended 
with  accumulation  of  mononuclear  leucocytes,  and  he  vaguely 
suggests  that  these  cells  may  be  endothelial  in  origin.  "  In 
discussing  this  phase  of  the  subject  it  is  proper  to  liken  the 
focal  necroses  and  the  preliminary  vessel  changes  to  the 
alterations  caused  by  the  so-called  '  endothelial  toxins  ' ; 
furthermore,  to  recall  that  some  such  toxins,  it  is  believed, 
are  liberated  from  the  bodies  of  bacteria." 

Le  Count  also  noted  in  the  spleen  of  guinea-pigs  and  man, 
but  not  in  monkeys,  the  presence  of  large  multinucleated 
cells  resembling  the  megakaryocytes  of  bone  marrow.  In  en- 
larged lymph  nodes  he  found  the  sinuses  crowded  with  mono- 
nuclear phagocytes.  No  lesions  were  found  in  the  bone 
marrow  of  animals  or  in  the  central  nervous  system  of  man 
and  animals. 

Perivascular  accumulations  of  cells  and  "  evidence  of  their 
multiplication  in  situ  "  in  the  testes  of  guinea-pigs  and  monkeys 
was  interpreted  by  Le  Count  as  the  probable  "  formation 
of  new  depots  for  the  production  of  leucocytes  or  other  cells 
which  presumably  are  in  some  way  designed  to  play  some 
part  in  the  defensive  processes.  These  are  usually  in  peri- 
vascular situations  and  so  limited  to  the  regions  of  the  lymph 
channels  that  it  seems  unreasonable  to  ascribe  them  to  the 
focal  processes  of  blood-vessel  obstruction  and  their  sequences." 

Le  Count's  contribution  to  the  pathology  of  the  disease 
was  the  recognition  of  the  vascular  lesions,  but  he  apparently 
regarded  them  as  secondary  to  focal  lesions  beginning  in  the 
tissues. 


38  WOLBACH. 

Ricketts'  conception  of  Rocky  Mountain  spotted  fever  was 
obtained  wholly  from  gross  observations.  He  considered  it 
to  be  a  hemorrhagic  septicaemia.  Later,  in  his  work  on  typhus 
fever,  he  took  the  same  attitude  and  he  classed  both  diseases 
with  plague. 

3.  Attempts  to  demonstrate  a  parasite.  • —  The  work  of 
Wilson  and  Chowning  and  the  supposed  discovery  of  a  piro- 
plasma  has  been  referred  to  in  the  historical  review. 

Fricks-^  in  19 16  reported  the  finding  of  protozoan-like  bodies 
in  the  blood  of  spotted-fever  guinea-pigs.  These  bodies  were 
intracellular  (in  red  corpuscles)  and  free,  but  were  found 
only  after  the  blood  had  gone  through  several  long  procedures, 
including  defibrination,  centrifugalizing  for  fifteen  minutes, 
diluting  with  salt  solution  and  a  second  centrifugalizing  for 
six  hours.  The  bodies  were  found  in  smears  from  the  sediment 
stained  with  Giemsa's  stain,  and  are  described  as  "  bright 
red  granular  bodies,  singly  and  in  pairs,  highly  refractile, 
accompanied  by  larger  light  blue  bodies,  and  all  surrounded 
by  a  pale  blue  matrix,  the  whole  mass  being  rather  indistinct 
but  not  encountered  in  the  controls."  These  bodies  were 
very  small  in  size,  the  red  staining  ones  being  less  than  one 
micron  in  diameter,  the  blue  staining  ones  slightly  larger. 
Fricks  could  not  find  similar  bodies  in  controls  from  normal 
guinea-pigs  and  from  guinea-pigs  with  other  diseases. 

It  is  of  interest  to  note  that  Fricks,  who  has  made  extensive 
studies  of  spotted  fever,  did  not  find  the  lanceolate  organisms 
described  by  Ricketts  and  myself. 

Ricketts' ^^'^^  attempts  to  demonstrate  a  parasitic  micro- 
organism in  Rocky  Mountain  spotted  fever  resulted  in  the 
finding  of  a  minute  lanceolate  bipolar  organism  in  the  blood 
of  man,  guinea-pigs  and  monkeys.  Similar  organisms  were 
found  by  him  in  the  tissues  of  infected  ticks  and  in  the  eggs 
of  infected  ticks.  These  small  rods  were  agglutinated  by 
the  blood  from  immune  guinea-pigs.  Ricketts  found  similar 
bacillary  forms  in  the  tissues  and  eggs  of  non-infective  ticks. 
In  the  light  of  my  own  work  it  seems  certain  that  Ricketts 
saw  in  the  blood  of  infected  animals  and  man  the  true  parasite 


ROCKY    MOUNTAIN    SPOTTED    FEVER.  39 

of  Rocky  Mountain  spotted  fever.  It  also  seems  certain 
that  in  the  tick  he  was  misled  by  bacteria  which  are  occasion- 
ally found  in  large  numbers  and  of  a  size  small  enough  to  make 
confusion  possible.  Ricketts  stated  that  the  bacilli  which 
he  regarded  as  the  cause  of  the  disease  were  found  in  enormous 
numbers  in  the  tissues  and  eggs  of  infected  and  non-infected 
ticks,  in  smear  preparations,  which  I  have  found  a  most 
unsatisfactory  method  for  demonstrating  the  true  parasite  of 
Rocky  Mountain  spotted  fever.  I  have  never  been  able  to 
find  the  parasite  in  any  number  in  eggs  from  proved  infected 
adult  ticks,  and  when  present  they  invariably  were  markedly 
different  in  their  morphology  from  those  described  by  Ricketts. 
I  have  had  the  opportunity  of  comparing  one  of  Ricketts' 
original  preparations  with  those  I  have  made  from  the  eggs 
of  infected  ticks,  and  from  the  eggs  of  non-infected  wild 
ticks,  and  feel  convinced  that,  while  Ricketts  may  have 
encountered  the  true  parasite  of  the  disease  in  ticks,  he  was 
led  hopelessly  astray  by  the  occurrence  of  bacteria  in  his 
infected  as  well  as  non-infected  ticks. 

VI.       IMMUNITY. 

No  instance  is  known  of  a  second  attack  of  Rocky  Mountain 
spotted  fever  in  man. 

Our  knowledge  of  experimental  immunity  in  animals  is 
derived  wholly  from  the  work  of  Ricketts  and  his  associ- 
ates^^'  ^^'  ^^'  ^®  upon  guinea-pigs.  Recovery  from  the  disease 
confers  a  complete  and  lasting  immunity  in  animals.  Passive 
immunity  may  be  conferred  by  the  injection  of  blood  from  an 
immune  animal  simultaneously  or  soon  after  the  injection 
of  the  virus,  but  this  immunity  is  not  lasting.  These  facts 
have  been  repeatedly  confirmed  by  my  own  experiments  upon 
guinea-pigs,  using  immune  guinea-pig  serum.  Attempts  to 
produce  passive  immunity  in  guinea-pigs,  using  serum  from 
immune  rabbits,  have  been  only  partly  successful  as  the 
experiments  were  much  interfered  with  by  the  presence  of 
an  epizootic  in  guinea-pigs  at  the  time;  but  there  are  no 
theoretical  reasons  why  immunity  should  not  be  conferred 
by  serum  from  immune  animals  of  another  species. 


40  WOLBACH. 

Ricketts  found  that  the  offspring  of  immune  female  guinea- 
pigs  were  immune  and  that  this  immunity  was  independent 
of  the  ingestion  of  milk  from  the  immune  mother,  and  also 
that  guinea-pigs  from  non-immune  parents  suckled  by  an 
immune  female  were  not  immune.  Experiments  done  by 
Foot^^  in  my  laboratory  on  the  offspring  of  the  immune 
rabbits  failed  to  demonstrate  the  presence  of  immunity. 

In  two  human  cases  studied  by  me,  Cases  i  and  3  of  this 
report,  two  were  given  transfusions  of  blood  from  an  immune- 
donor  who  had  recovered  from  the  disease  the  previous  year. 
No  beneficial  effects  were  observed,  but  the  tests  are  of  small 
value  as  the  transfusions  were  done  late  in  the  course  of  the 
disease. 

VII.       THE  ROCKY  MOUNTAIN  SPOTTED  FEVER  TICK. 

I.  Nomenclature.  —  It  is  now  recognized  that  but  one 
species  of  Dermacentor  is  concerned  in  the  natural  trans- 
mission of  Rocky  Mountain  spotted  fever.  When  Ricketts 
began  his  work,  there  had  been  but  little  systematic  study 
of  ticks  from  the  northwest  region,  and  the  ticks  he  used 
from  the  Bitter  Root  Valley  were  identified  by  Stiles  as 
Dermacentor  occidentalis,  a  closely  similar  species.  Later, 
Stiles^^  recognized  the  Bitter  Root  tick  as  a  new  species  which 
he  named  Dermacentor  andersoni.  Meanwhile  Banks^  had 
described  this  tick  as  Dermacentor  venustus,  and  gave  Marx 
the  credit  for  this  name,  and  for  separating  it  from  D.  occi- 
dentalis. For  a  time  the  ticks  concerned  in  the  transmission 
of  the  disease  in  Idaho  were  erroneously  regarded  by  Banks 
as  a  distinct  species,  Dermacentor  modestus,  and  Ricketts^^ 
used  this  name  in  speaking  of  the  ticks  from  Idaho. 

These  various  names  have  all  been  used  loosely  by  authors 
in  writing  about  Rocky  Mountain  spotted  fever,  and  naturally 
confusion  has  existed  as  to  the  correct  nomenclature,  even 
among  entomologists,  and  whether  or  not  more  than  one  tick 
is  concerned  in  the  transmission  of  the  disease. 

Stiles  protested  against  the  use  of  the  name  Dermacentor 
venustus  for  the  spotted  fever  tick,  believing  that  Doctor  Marx 
intended  it  for  a    species    of   Dermacentor  from  Texas.     Be 


ROCKY    MOUNTAIN    SPOTTED    FEVER.  41 

this  as  it  may,  there  is  no  question  at  all  in  regard  to  the 
identity  of  the  ticks  used  by  Banks  and  by  Stiles  in  their 
studies  and  Dermacentor  venuskcs,  Banks,  and  Dermacentor 
andersoni,  Stiles,  are  identical. 

When  systematists  arraign  one  another  in  controversy  in 
spite  of  the  International  Code,  a  novice  had  best  refrain 
from  comments,  but  a  brief  statement  of  the  situation  seems 
advisable  in  the  face  of  the  confusion  in  regard  to  the  proper 
name  or  names  of  the  tick  concerned  and  whether  or  not 
more  than  one  tick  may  be  the  subject  of  this  confusion. 

Banks'^  in  1910  protested  against  the  name  Dermacentor 
andersoni,  rightly  claiming  that  he  was  the  first  to  separate 
the  tick  in  question  from  D.  occidentalis,  giving  it  the  name 
D.  veniistus,  a  manuscript  name  from  Marx.  Stiles'^'*  in 
answer  claimed  that  D.  venustus  was  applied  by  Marx  to  a 
different  species  and  that  the  name  was  originally  published 
by  Neumann  in  1897  as  a  synonym  of  D.  reticulatus,  and  its 
typical  locality  was  given  as  Texas  and  New  Mexico.  This 
view  of  Stiles  was  also  that  of  Salmon  and  Stiles^^  in  regard 
to  D.  venustus  in  1900  before  the  identification  of  the  spotted 
fever  tick  as  a  new  species  was  made. 

Banks'*  in  1908,  in  his  description  of  Dermacentor  venustus y. 
says:  "  This  species  is  quite  common  in  the  Northwest. 
It  has  been  included  in  D.  occidentalis  by  Neumann,  but  was 
separated  out  by  Doctor  Marx  in  manuscript  under  the  name 
I  have  adopted.  This  is  the  species  supposed  to  be  concerned 
in  the  transmission  of  spotted  fever  in  Montana."  Banks 
gave  the  sources  of  his  specimens  of  D.  ve7tustus  as  Washington, 
Colorado,  New  Mexico,  Montana,  Utah,  Idaho  and  Texas  (on 
sheep). 

We  may  therefore  assume  that  Banks  believed  that  the 
tick  described  in  manuscript  as  D.  venustus  by  Marx  was 
neither  D.  reticulatus  nor  D.  occidentalis,  but  was  identical 
with  specimens  later  obtained  by  him  (Banks)  from  the  North- 
west and  identical  with  the  tick  subsequently  described  by 
Stiles  as  D.  andersoni. 

Usage  is  settling  the  difficulty  in  favor  of  D.  venustus.. 
Patton  and  Cragg'*''  in  their  textbook  of  Medical  Entomology 


42  WOLBACH. 

use  the  name  D.  andersoni.  R.  O.  Newmann  and  Mayer, ^^  in 
Lehmann's  "  Atlas  und  Lehrbuch  wich tiger  tierischer  Para- 
■siten  und  ihrer  Uebertrager,"  accept  D.  venustus.  Theobald* 
in  "  The  Animal  Parasites  of  Man,"  by  Fantham,  Stephens 
and  Theobald,^^  also  uses  D.  venustus  to  designate  the  spotted 
fever  tick.  Nuttall^^  uses  D.  venustus  in  describing  the  habits 
of  this  tick,  but  in  a  footnote  states  that  the  name  is  "  still 
sub  judice." 

The  name  D.  venustus  is  used  in  the  publications  of  the 
Federal  Bureaus  of  Entomology  and  Biological  Survey  and 
by  the  Montana  State  Board  of  Entomology. 

There  is  now  no  excuse  for  confusion  in  regard  to  the  tick 
itself.  Dermacentor  occidentalis  is  another  species  with  a  more 
Avestern  habitat  which  does  not  overlap  that  of  D.  venustus 
(Birdseye,^  Hunter  and  Bishopp^^)  and  is  easily  distinguishable 
from  D.  venustus.  Dermacentor  modestus,  other  than  in  the 
publications  of  Ricketts,  has  not  figured  in  literature  and 
is  not  to  be  found  in  any  entomological  publication  I  have 
consulted,  and  may  be  regarded  as  a  name  applied  to  speci- 
mens of  D.  venustus  from  Idaho,  for  a  time,  under  the  im- 
pression that  they  represented  a  new  species. 

In  this  paper  Dermacentor  venustus  will  be  used  as  the 
name  of  the  spotted  fever  tick;  synonym,  —  Dermacentor 
andersoni. 

2.  The  classification  and  external  anatomy  of  ticks.  Figs. 
8  to  17.  — A  brief  consideration  of  the  classification  of  ticks, 
super  family  Ixodoidea,  order  Acarina,  class  Arachnida,  in 
general  is  essential  in  this  report  because  of  the  desirability 
of  clearing  away  the  confusion  which  exists  in  foreign  medical 
works  on  entomology  in  regard  to  the  conveyor  of  spotted 
fever.  A  brief  description  of  the  anatomy  of  ticks  is  accord- 
ingly given  for  the  purpose  of  making  intelligible  the  principles 
of  classification. 

The  ticks  are  visible  to  the  naked  eye  in  all  stages  and 
several  different  stages  are  recognized  in  each  species;  the 
eggs  which  are  ovoid  with  a  tough,  almost  transparent,  pliable 
shell;    the  larvae  which  are  six-legged  and  without  genitalia; 


ROCKY   MOUNTAIN    SPOTTED    FEVER.  43 

the  nymphs  which  are  eight-legged  and  also  asexual,  and  the 
adults,  which  also  have  eight  legs  and  which  are  sexually 
mature  as  male  or  female. 

Ticks  have  a  body  and  a  capitulum  or  rostrum,  popularly 
spoken  of  as  a  head.  The  true  head  of  a  tick  has  become 
fused  with  the  body  and  cannot  be  recognized.  There  is  no 
cephalothorax.  The  capitulum  consists  of  a  base,  the  basis 
capituli,  which  bears  the  palps,  the  manibles  or  chelicerae, 
the  mandibular  sheaths  and  the  hypostome,  radula  or  labio- 
maxillary  dart.  The  mandibles  with  their  sheaths  and  the 
hypostome  form  the  proboscis  or  haustellum. 

The  basis  capituli  is  the  basal  portion  which  articulates 
with  the  body  in  the  recess  or  emargination  called  the  cameros- 
tome.  Its  shape  varies  in  different  species,  and  hence  it  is 
of  value  in  classification.  In  females  the  basis  capituli 
contains  on  each  side  of  a  median  ridge  a  depressed  area 
which  consists  of  many  minute  pores  and  which  are  known 
as  the  porose  areas.  As  the  shape  and  precise  position  of 
these  areas  vary  in  different  species,  they  are  also  of  value 
in  classification. 

The  hypostome  is  situated  in  the  median  line  and  consists 
■of  two  fused  symmetrical  halves  forming  an  elongated, 
spatulate,  chitinous  structure  armed  with  small  teeth  which 
are  directed  backwards  and  arranged  in  transverse  rows. 
The  arrangement,  size  and  distribution  of  the  teeth  vary  in 
different  species. 

The  paired  mandibles  and  their  sheaths  form  the  dorsal 
wall  of  the  organ  of  penetration  of  which  the  hypostome 
forms  the  ventral  wall.  The  mandibles  consist  of  cylindrical 
pieces  or  shafts  of  chitin,  the  proximal  ends  of  which  are 
bulbous  and  project  into  the  body  cavity  to  receive  the 
attachments  of  the  extensor  and  retractor  muscles.  On  the 
distal  ends  of  each  mandible  is  articulated  a  digit  which  bears 
two  or  three  toothed  apophyses.  Although  the  digits  vary 
in  architecture  in  different  species,  they  are  not  of  especial 
value  in  classification. 

The  mandibular  sheaths  are  dorsal  to  the  mandibles  and 
•continuous  with   the  anterior  portion  of  the  basis  capituli. 


44  WOLBACH. 

The  two  sheaths  lie  in  close  apposition;  their  distal  ends  form 
thin  membranes  which  are  invaginated  and  attached  to  the 
shafts  of  the  mandibles.  The  outer  surfaces  of  the  sheaths 
are  covered  with  teeth  of  microscopic  size  arranged  in  rows. 

The  palpi  are  inserted  deeply,  one  on  each  side,  into  the 
basis  capituli  on  the  antero-lateral  margins,  in  some  species 
more  on  the  dorsal  side,  in  others  more  on  the  ventral  side. 
They  are  flap-like  structures  composed  of  four  segments,  and 
vary  considerably  in  size  and  shape  in  the  different  species 
of  ticks.  The  basal  segment  is  short  and  broad  and  usually 
hidden  by  the  basis  capituli,  while  the  distal  segment  is  very 
small  so  that  commonly  only  two  segments  are  easily  seen. 
The  palps  as  a  whole  are  concave  on  the  median  side  and  serve 
to  sheath  the  mouth  parts.  The  comparative  dimensions 
of  the  second  and  third  segments  of  the  palpi  are  of  value  in 
classification. 

The  body  is  oval  or  elliptical,  flat  in  shape  dorso-ventrally^ 
and  the  dorsal  surface  is  slightly  convex.  The  anterior  end 
of  the  body  is  emarginated  to  form  the  camerostome  into 
which  the  capitulum  is  articulated.  The  integument  as  a 
whole  is  pliable,  tough  and  leathery. 

In  Ixodidae  the  dorsal  surface  is  covered  with  a  hard, 
chitinous  plate  of  varying  shape,  usually  irregularly  hexagonal,, 
called  the  scutum.  In  the  male  the  scutum  covers  almost 
the  whole  dorsal  surface;  in  the  female  it  covers  only  about 
the  anterior  half  though  after  engorgement  it  becomes  very 
much  smaller  in  proportion  to  the  size  of  the  tick.  The 
scutum  is  usually  marked  by  two  longitudinal  cervical  grooves. 
The  eyes,  when  present,  are  situated  on  the  lateral  margins 
of  the  scutum.  The  festoons  are  small  lobe-like  portions 
of  the  posterior  margin  of  the  body,  usually  eleven  in  number,, 
which  are  bounded  by  short  furrows  running  inwards  from 
the  body  margin. 

On  the  ventral  surface  of  the  body  there  are  two  orifices 
in  the  median  line,  a  genital  aperture  or  pore,  situated  ante- 
riorly close  to  the  base  of  the  capitulum  and  the  anus  situated 
posterior  to  the  last  pair  of  legs.  The  anus  is  surrounded  by 
a   groove   which    is   of   great   importance   in    classifying   the 


ROCKY    MOUNTAIN    SPOTTED    FEVER.  45 

several  genera  as  it  varies  in  position  and  shape.  The  males 
of  some  species  have  one  or  two  chitinous  plates  on  each 
side  of  the  anus,  also  of  importance  in  classification. 

The  legs  arise  from  the  anterior  part  on  each  side  of  the 
ventral  surface  and  each  leg  consists  of  six  parts  or  segments. 
The  coxa  is  the  basal  or  first  segment;  it  lies  flat  against  the 
body  and  is  not  movable;  it  may  have  one  or  two  spurs, 
i.e.,  dentate  or  bidentate.  The  next  segment  is  the  tro- 
chanter, which  is  short  and  may  be  broader  than  long.  The 
third  segment  is  the  femur,  which  is  elongated  and  joined 
to  the  trochanter  by  a  pseudo-articulation.  The  fourth 
•segment,  the  tibia,  and  the  fifth,  protarsus  or  metatarsus, 
are  also  elongated.  The  sixth  segment,  or  tarsus,  may  also 
at  its  proximal  end  form  a  pseudo-articulation;  its  extremity 
is  provided  with  two  claws  supported  by  a  long  or  short  stalk. 
In  the  Ixodidse  the  claws  carry  on  their  ventral  surface  a 
membranous  disc-like  or  umbrella-like  expansion,  the  pul- 
villum.  Haller's  organ  is  situated  on  the  dorsal  surface  of 
the  first  (anterior)  coxa;  it  consists  of  several  cup-shaped 
pores  containing  sensory  hairs  and  dermal  cells.  It  is  supposed 
to  be  an  organ  of  hearing  (Banks)  or  smell  (Patton  and  Cragg). 

The  stigmal  plates  containing  the  spiracles  or  stigmal 
■orifices  into  which  the  tracheae  open,  consist  of  raised  chitinous 
plates  traversed  by  goblet-like  structures  which  give  the 
surface  a  reticulated  appearance.  The  stigmal  plates  may 
be  round,  oval,  triangular  or  comma-shaped,  and  the  shape 
and  markings  are  quite  constant  for  each  species,  though 
they  differ  in  the  sexes.  The  stigmal  plates  are  situated 
above  and  usually  behind  the  last  (fourth)  coxa. 


46 


WOLBACH. 


The  ticks  Ixodoidea  are  divided  into  two  families,  the 
ArgasidcB  and  the  Ixodidcz,  the  most  striking  difference  be- 
tween the  two  famihes  being  the  possession  of  a  shield  or 
scutum  by  the  latter.  Other  differences  as  tabulated  by 
Nuttall,  Warburton,  Cooper  and  Robinson^^  are: 


Argasid^. 

IXODID^. 

Sexual  dimor- 
phism    .... 

Slight. 

Marked. 

Capitulum: 

Base   ..... 

Ventral  camerostome,  no 
porose  areas  in  9  • 

Anterior  camerostome,  po- 
rose areas  in   9  ■ 

Palps      .    .    .    . 

Leg-like   with    sub-equal 
articles. 

Relatively   rigid,    of   very 
varied    form,   with    rudi- 
mentary fourth  article. 

Body: 

Scutum       .    .    . 

Festoons    .    .    . 

Absent. 
Absent. 

Present. 
Generally  present. 

Eyes: 

(When  present) 

Lateral  on   supracoxal 
folds. 

Dorsal  on  sides  of  scutum. 

Spiracles. 

Very  small,  more  anterior. 

Generally   large,   well   be- 
hind Coxa  IV. 

Legs: 

Coxa 

Tarsi 

Unarmed. 
Without  ventral  spurs. 

Generally     armed     with 

spurs. 

Generally  armed  with  one 
or  two  ventral  spurs. 

Pad     (pulvillus)    . 

Absent  or  rudimentary. 

Always  present. 

There  are  two  genera  of  ArgasidcB,  Argas  and  Ornithodorus. 

There  are  several  classifications  of  the  IxodidcB.  The 
following  by  Nuttall,  Warburton^^  et  al.  will  serve  the  purposes 
of  this  paper;  it  carries  the  weight  of  great  authority  and  has 
been  logically  developed  along  established  lines.  The  reader 
is  referred  to  the  work  of  Patton  and  Cragg^^  for  a  comparison 
of  several  classifications. 


ROCKY   MOUNTAIN    SPOTTED    FEVER. 
Ixodidae 


Prostriata  (anal  grooves  surround- 
ing the  anus  in  front). 


Ixodes 


Brevirostrata 
(short  capitulum) 


47 


Metastriata    (anal   grooves    curve 
about  the  anus  posteriorly j. 


Longirostrata 
(long  capitulum) 


Group  I  Group  2 


Hemaphysalis.    Dermacentor. 
Rhipicentor. 
Rhipicephalus. 
Margopus. 
Boophilus. 


Group  I  Group  2 


Hyaloma.      Amblyoma. 
Aponomma. 


The  genus  Dermacentor  is  defined  as:  "  usually  ornate 
with  eyes  and  festoons;  with  short,  broad  or  moderate  palps 
arid  basis  capituli  rectangular  dorsally.  In  some  species 
Coxse  I.  to  IV.  of  the  male  increase  progressively  in  size; 
in  all  species  Coxa  IV.  is  much  the  largest;  the  male,  more- 
over, shows  no  ventral  plate  or  shields,  Coxa  I.  bifid  in  both 
sexes.     Spiracles  sub-oval  or  comma-shaped." 

The  original  description  of  Dermacentor  venustiis  by  Banks  ^ 
is  as  follows: 

"  Male.  Red-brown,  marked  with  white,  but  not  so  extensively  as 
D.  occidentalis,  usually  but  little  white  on  the  middle  posterior  region; 
legs  paler  red-brown,  tips  of  joints  whitish.  Capitulum  quite  broad, 
its  posterior  angles  only  slightly  produced;  palpi  very  short  and  broad, 
with  many,  not  very  large  punctures;  lateral  furrows  distinct.  Legs  of 
moderate  size,  hind  pair  plainly  larger  and  heavier,  and  with  the  teeth 
distinct.  Coxae  armed  as  usual,  the  Coxa  IV.  nearly  twice  as  wide  at  base 
as  long.  Stigmal  plate  with  a  rather  narrow  dorsal  prolongation,  with 
large  granules  in  the  main  part  and  minute  ones  on  the  prolongation. 
Length  of  male  3.5  to  5  mm." 

"  Female.  Capitulum  and  legs  reddish-brown,  the  latter  with  tips  of 
joints  whitish;  shield  mostly  covered  with  white.  This  white  not  so 
much  broken  up  by  the  brown  dots  as  in  D.  occidentalis;  abdomen  red- 
brown.  Capitulum  rather  broad,  posterior  angles  but  little  produced, 
the  porose  areas  rather  large,  egg  shaped,  and  quite  close  together;  palpi 
shorter  than  width  of  capitulum.     Shield  as  broad  as  long,  broadest  slightly 


48  WOLBACH. 

before  its  middle,  and  rather  pointed  behind,  with  numerous,  not  very 
large  punctures.  Legs  of  moderate  size,  the  coxae  armed  as  usual.  The 
stigmal  plate  has  a  rather  narrow  dorsal  prolongation,  with  large  granules 
on  the  main  part,  and  small  ones  on  the  prolongation.  Length  of  female 
shield  2  mm." 

Banks  makes  the  following  comment:  "This  species  is 
quite  common  in  the  Northwest.  It  has  been  included  in 
D.  occidentalis  by  Neumann,  but  was  separated  out  by  Dr. 
Marx  in  manuscript  under  the  name  I  have  adopted.  It  is 
larger  than  D.  occidentalis ,  with  more  red  and  less  white  in 
the  coloring,  and  differs  in  many  minor  points  of  structure, 
such  as  size  of  porose  areas,  size  of  hind  coxae  in  male,  etc. 
This  is  the  species  supposed  to  be  concerned  in  the  trans- 
mission of  spotted  fever  in  Montana." 

3.  Hosts  of  Dermacentor  venustus.  —  Besides  the  domestic 
animals  which  graze,  such  as  horses,  cows,  mules,  asses, 
sheep  and  goats,  practically  all  of  the  wild  mammals  of  the 
tick-infested  regions  serve  as  hosts.  Facts  which  are  of 
interest  and  of  probable  importance  in  the  distribution  of 
the  virus  in  nature  are  that  the  larvae  and  nymphs  of  the 
tick  feed  exclusively  upon  small  animals  and  that  the  adults 
feed  chiefly  upon  larger  animals  and  in  settled  regions 
largely  upon  horses,  cattle  and  sheep.  According  to  Parker,''^ 
the  domestic  pig  occasionally  serves  as  host. 

Hunter  and  Bishopp^''  found  larvae  or  nymphs  or  both  upon 
the  following  animals: 

Common  names.  Scientific  names. 

Columbian  ground  squirrel  Cilellus  columhianus 

Yellow-bellied  chipmunk  Eutamias  b.  luteiventris 

Pine  squirrel  Sciurus  h.  richardsoni 

Woodchuck  Marmota  flaviventer 

Side-striped  ground  squirrel  Callospermophilus  I.  cinerascens 

Wood  rat  Neotoma  cinerea 

Snowshoe  rabbit  Lepus  hairdi 

Cottontail  rabbit  Sylvilagus  nuttalli 

White-footed  mouse  Peromyscus  m.  artemisicB 

White-bellied  chipmunk  Eutamias  q.  umbrinus 

Large  meadow  mouse  Microtus  modestus 

Jumping  mouse  Zapus  princeps 

Pika  or  rock  rabbit  Ochotona  princeps 

Pocket  gopher  Thomomys  fuscus 


ROCKY   MOUNTAIN    SPOTTED    FEVER.  49 

The  woodchuck,  jack  rabbit  and  snowshoe  rabbit  also 
Tiarbored  adult  ticks,  while  adults  only  were  found  on  the 
following: 

Common  names.  Scientific  names. 

Mountain  goat  Oreamnos  monlanus 

Brown  bear  Ursus  americanus 

Coyote  Canis  lestes 

Badger  Taxidea  taxus 

Wild  cat  Lynx  uinta 

Dermacentor  venustus  was  not  found  on  the  white-tailed 
•deer  (Odocoileus  leucurus),  two  specimens;  the  mule  deer 
{Odocoileus  hemionns),  six  specimens,  and  the  elk  (Cervus 
■canadensis),  one  specimen. 

Parker  and  Wells'*^  in  eastern  Montana  found  larva;  or 
nymphs  or  both  on  the  following  animals:  ' 

Common  names.  Scientific  names. 

Prairie  dog  Cynomys  ludovicianus 

Jack  rabbit  Lepus  toicnsendi  campanius 

Cottontail  rabbit  Sylvilagus  nuttalli  grangeri 

Striped  spermophile  Citellus  tridecemlineatus  pallidus 

Kangaroo  rat  Perodipus  montanus  richardsoni 

Pack  rat  Neotoma  cinerea 

Upland  meadow  mouse  Microtus  ochrogaster  haydeni 

Grasshopper  mouse  Onychomys  leucogaster  missouriensis 

Deer  mouse  Peromyscus  mamiculafus  osgoodi 

Pale  chipmunk  Eutamias  pallidus 

Porcupine  Erethizon  epixanthus 

Adult  ticks  were  also  found  on  the  prairie  dog,  jack  rabbit 
and  porcupine. 

In  western  Montana  the  mountain  goat  seems  to  be  the 
most  important  wild  host  of  the  adult  D.  venustus,  as  over 
a  hundred  in  various  stages  up  to  complete  engorgement 
were  found  on  each  of  three  goats  examined.  The  most 
important  host  of  the  larvae  and  nymphs  is  the  ground  squirrel, 
as  sixty-five  per  cent  of  three  hundred  and  forty-one  examined 
were  tick  infested.  Next  in  order  of  importance  as  hosts 
for  larvae  and  nymphs  are  the  yellow-bellied  chipmunk  and 
the  pine  squirrel.  Other  mammals  of  considerable  importance 
are  the  woodchuck,  snowshoe  rabbit,  wood  rat,  white-footed 
mouse,  meadow  mouse  and  side-striped  ground  squirrel. 


50  WOLBACH. 

In  eastern  Montana  the  jack  rabbit  is  the  most  important 
wild  host  of  the  adult  spotted  fever  tick,  as  Parker^^  found 
eighty-seven  per  cent  of  them  infected  (eighty-four  specimens 
examined).  The  jack  rabbit  also  harbors  the  nymph  and  the 
larva;  it  is  the  most  important  host  of  nymphs  in  eastern 
Montana,  and  is  the  only  animal  that  acts  as  host  to  all 
three  stages  of  this  tick.  The  deer  mouse,  as  a  host,  is  next 
in  importance  in  eastern  Montana,  because  of  its  abundance 
and  because  it  harbors  both  larvae  and  nymphs. 

4.  Biology  of  Dermacentor  venustiis.  The  following  account 
is  taken  chiefly  from  the  papers  by  Hunter  and  Bishopp^®'  ^'^ 
and  Bishopp  and  King.'^ 

This  tick,  in  cornmon  with  most  other  ticks,  passes  through 
four  distinct  stages,  the  egg,  the  larva,  the  nymph  and  the 
adult.  Fully  engorged  females  deposit  from  two  thousand 
to  four  thousand  eggs.     These  hatch  into  six-legged  larvae. 

The  larvae  feed  on  small  mammals  and  require  three  to 
eight  days  for  complete  engorgement.  When  engorged  they 
drop  from,  the  host  and  seek  protected  places,  and  in  a  few 
days  become  quiescent.  After  a  quiescent  period  of  six  tO' 
twenty-one  days  (Hunter  and  Bishopp)  or  eleven  to  thirty- 
one  days  after  dropping  (Bishopp  and  King)  the  eight-legged 
asexual  nymphs  emerge. 

The  nymphs  in  natural  conditions  may  pass  the  winter 
either  in  the  unengorged  or  engorged  state.  Engorgement 
is  necessary  as  in  the  case  of  the  larvae,  for  further  develop- 
ment, and  again  the  hosts  are  small  mammals,  the  same 
that  the  larvae  feed  upon.  The  nymphs  require  three  tO' 
nine  days  for  feeding,  and  leave  the  host  after  engorgement 
and  according  to  the  temperature,  molt  to  sexually  mature 
adults  in  from  twelve  to  one  hundred  and  forty  days.  Nymphs 
will  pass  the  winter  in  the  engorged  state  and  in  experiments 
made  by  King  in  1910-11  nymphs  engorged  between  August 
22  and  September  11  emerged  as  adults  between  July  26 
and  August  18,  191 1,  giving  a  maximum  period  for  molting 
of  eleven  months  and  nineteen  days.  In  other  experiments 
by  King  in  the  Bitter  Root  Valley  in   191 1,  nymphs  which 


ROCKY    MOUNTAIN    SPOTTED    FEVER.  5 1 

engorged  in  April  molted  in  eighty-three  to  one  hundred  and 
forty  days,  those  engorged  in  May  molted  in  seventy-three 
to  ninety-nine  days,  those  engorged  in  June  molted  in  thirty- 
nine  to  sixty-four  days,  those  engorged  in  July  molted  in 
twenty-nine  to  sixty-one  days,  and  those  engorged  in  August 
molted  in  twenty-seven  to  thirty-one  days. 

The  adult  ticks  feed  in  the  spring  months  before  hot  weather 
begins  and  almost  wholly  on  large  animals  such  as  horses 
and  cattle.  The  males  after  feeding  about  four  days  seek 
the  females  which  are  fertilized  while  feeding.  It  requires 
eight  to  fourteen  days  for  the  female  to  engorge,  after  which 
she  drops  from  the  host  and  finds  a  protected  spot  in  which 
to  deposit  her  eggs.  The  period  before  the  deposition  of 
eggs  begins  after  engorgement,  varies  with  the  temperature; 
at  Dallas,  Texas,  Hunter  and  Bishopp,  with  eight  females, 
record  periods  of  from  six  to  ten  days.  In  the  Bitter  Root 
Valley,  with  three  females,  they  record  periods  of  thirteen 
to  forty-one  days  in  1910,  while  Bishopp  and  King  in  the 
Bitter  Root  Valley  during  a  colder  spring,  191 1,  with  seven 
females  record  periods  between  twenty  and  fifty-nine  days. 
The  female  dies  within  a  few  days  after  depositing  the  last 
eggs,  which  are  all  in  one  place  as  she  is  inactive  during  the 
process. 

Temperature  conditions  also  affect  the  incubation  period 
of  the  eggs,  sixteen  to  thirty-five  days  with  eight  batches  of 
eggs  at  Dallas,  Texas,  are  periods  given  by  Hunter  and 
Bishopp,  while  in  1910  in  the  Bitter  Root  Valley  with  four 
batches  of  eggs,  the  periods  were  thirty-four  to  fifty-one 
days.  In  191 1  Bishopp  and  King  with  seven  batches  of 
eggs  obtained  incubation  periods  of  thirty-one  to  seventy- 
three  days. 

The  entire  life  cycle  of  the  tick  under  natural  conditions 
requires  two  years,  but  may  take  three  years,  as  unfed  nymphs 
and  adults  may  survive  for  long  periods.  King  (personal 
communication)  has  demonstrated  that  adult  ticks  may  not 
find  opportunity  for  feeding  until  the  fourth  spring  from  the 
egg  stage.     Larvae,  nymphs  and  adult  ticks  all  m^ay  hibernate 


52  WOLBACH. 

in  the  unfed  condition.  Larvae  may  live  more  than  three 
hundred  and  seventeen  days,  nymphs  more  than  a  year, 
and  adults  more  than  six  hundred  and  thirty-two  days  in 
the  unfed  condition.  Adult  ticks  which  do  not  engorge 
before  hot  weather  sets  in  leave  the  plants  upon  which  they 
rest  while  awaiting  hosts  and  crawl  down  beneath  grass  and 
leaves  to  await  another  season,  remaining  practically  inactive 
until  hibernation,  so  that  after  July  first  very  few  adult  ticks 
are  seen  in  the  Bitter  Root  Valley. 

The  greatest  abundance  of  adult  ticks  is  during  April  and 
May,  and  they  disappear  rapidly  from  sight  during  June, 
so  that  by  July  first  few  are  found  attached  to  hosts.  Their 
first  appearance  after  hibernation  depends  upon  the  tem- 
perature; Bishopp  and  King  estimate  that  a  daily  mean 
temperature  of  38°  F.  to  42°  F.  for  six  to  twelve  days  will 
cause  the  ticks  to  emerge  from  hibernation,  so  that  the  second 
week  of  March  begins  the  activities  of  the  ticks  in  all  of  the 
states  where  spotted  fever  exists. 

Dormancy  in  the  fall  is  induced  by  temperatures  con- 
siderably higher,  10°  F.  to  15°  F.  (Bishopp  and  King)  than 
that  required  to  awaken  the  ticks  from  hibernation,  which 
means  late  August  to  early  September  in  the  spotted  fever 
states.  The  nymphs  and  larvae  probably  enter  hibernation 
at  the  same  time,  as  their  principal  hosts,  the  ground  squirrel 
and  woodchuck,  go  into  hibernation  about  the  middle  of 
August. 

The  life  cycle,  as  has  been  stated  above,  requires  naturally 
at  least  two  years.  Bishopp  and  King  have  shown  that 
nymphs  which  develop  from  over-wintered  adults  do  not 
engorge  that  year,  and  also  that  adults  which  develop  from 
over-wintered  nymphs  do  not  engorge  the  same  year.  There- 
fore eggs  are  deposited  only  by  ticks  which  have  passed  the 
winter  in  the  adult  stage,  and  the  eggs  do  not  develop  beyond 
the  nymphal  stage. 

The  ordinary  life  cycle  is  probably  as  follows:  —  Larvae 
and  nymphs  which  pass  the  winter  engorged  or  unengorged, 
reach  the  adult  stage  the  following  summer.  Adults  which 
pass  the  winter  deposit  eggs  the  following  spring,  and  their 


ROCKY   MOUNTAIN    SPOTTED    FEVER.  53 

eggs  may  develop  as  far  as  the  nymphal  stage.  As  adults 
very  frequently  do  not  find  hosts  the  first  season,  a  three-year 
cycle  cannot  be  uncommon. 

In  the  laboratory,  ticks  may  be  reared  from  eggs  the  same 
season  they  are  deposited.  The  history  of  the  eggs  from 
two  females  received  engorged  from  R.  R.  Parker,  in  June, 
1918,  is  as  follows: 

Female  A.  Deposited  eggs  between  June  21  and  June  30. 
Eggs  hatched  at  room  temperature  July  20  to  July  29.  The 
larvae  were  placed  on  a  guinea-pig  on  August  i  and  dropped 
fully  engorged  between  August  5  and  August  8.  The  larvje 
molted  to  nymphs  between  August  18  and  August  23,  and 
were  fed  on  a  guinea-pig  between  September  18  and  27. 
The  engorged  nymphs  were  placed  in  a  bacteriological  in- 
cubator at  37.5°  C.  September  27.  The  majority  of  them 
molted  to  adults  between  October  19  and  December  4. 

Female  B.  Received  engorged  from  R.  R.  Parker  in 
June,  1918,  and  deposited  eggs  between  June  21  and  June  30. 
The  larvse  emerged  at  room  temperature  between  July  20 
and  July  29,  and  were  placed  upon  a  guinea-pig  on  August  5. 
The  fully  engorged  larvse  dropped  between  August  8  and 
August  12,  and  were  kept  at  room  temperature.  The  nymphs 
emerged  between  August  21  and  August  28.  They  were  fed 
between  September  18  and  September  26.  Four  fully  en- 
gorged nymphs  only  were  recovered,  and  these  were  placed 
in  the  bacteriological  incubator  at  37.5°  C.  The  first  molted 
on  October  22;  two  more  between  this  date  and  December 
3;  one  perished. 

5.  Susceptibility  of  wild  mammals  to  Rocky  Mountain 
spotted  fever.  —  Ricketts^^-  ^^  proved  the  susceptibility  of 
the  ground  squirrel  {Citelliis  columhianus) ,  the  woodchuck 
{Marmota  flaviv enter) ,  the  rock  squirrel  {Callospermophiliis 
lateralis  cinerascens) ,  the  chipmunk  (Eutamias  sp.?),  and  the 
mountain  rat  {Neotoma.sp.?). 

McClintic^^  showed  that  the  ground  squirrel  (C.  colum- 
hianus), the  badger  (Taxidea  taxus),  the  weasel  {Putoriiis 
arizonensis) ,   the  woodchuck   (Marmota  flaviventer) ,  and  the 


54  WOLBACH. 

rock  squirrel  (Callospermophilus  lateralis  cinerascens)  could 
be  infected.  All  showed  only  slight  evidence  of  the  disease, 
and  guinea-pig  inoculation  was  necessary  in  each  instance 
to  prove  the  presence  of  the  virus  in  the  blood  of  the  animals 
tested.  McClintic  also  proved  that  immune  ground  squirrels 
and  woodchucks  existed  in  the  Bitter  Root  Valley.  Of  one 
hundred  and  sixty  ground  squirrels,  forty  were  incapable  of 
maintaining  the  virus  when  inoculated  from  infected  guinea- 
pigs.  Of  fifteen  woodchucks,  three  were  found  to  be  in- 
capable of  maintaining  the  virus.  The  demonstration  of 
immune  ground  squirrels  and  woodchucks  is  strong  evidence 
that  these  animals  are  infected  in  nature  by  the  bites  of  ticks. 

6.  Infected  ticks  in  nature.  —  Ricketts^^  was  the  first  to 
produce  spotted  fever  in  a  guinea-pig  by  allowing  wild  ticks, 
D.  venustus,  to  feed  upon  it.  In  one  experiment  in  which 
thirty-six  male  ticks  from  the  Bitter  Root  Valley  were  fed 
upon  one  guinea-pig,  a  typical  case  of  spotted  fever  resulted. 
Later  Maver^^  produced  the  disease  in  two  out  of  fourteen 
guinea-pigs,  upon  each  of  which  twenty-five  male  and  twenty- 
five  female  ticks  were  allowed  to  feed.  Nine  of  these  guinea- 
pigs  had  Montana  ticks  from  the  region  of  the  Bitter  Root 
Valley  and  five  Idaho  ticks  from  the  vicinity  of  Pocatello 
placed  upon  them.  At  the  time  of  the  experiment  the  Idaho 
ticks  were  erroneously  regarded  as  distinct  from  D.  venustus 
and  were  called  D.  modestus.  Two  of  the  guinea-pigs  upon 
which  ticks  from  the  Lo  Lo  Valley  (a  tributary  of  the  Bitter 
Root  Valley)  were  fed,  developed  spotted  fever.  The  ticks 
used  were  collected  from  cows.  The  guinea-pigs  upon  which 
the  Idaho  ticks  were  fed  did  not  develop  spotted  fever. 

McClintic  made  more  extensive  researches  in  this  direction, 
the  results  of  which  were  published  after  his  death  by  Fricks.^" 
About  two  thousand  ticks,  D.  venustus,  collected  in  the 
foothills  of  the  Bitter  Root  Mountains  west  of  Victor,  were 
used  and  were  fed  in  lots  of  varying  numbers  upon  fifty-four 
guinea-pigs.  Six  lots  of  these  ticks  were  collected  from 
mountain  goats.  In  all,  six  guinea-pigs  developed  spotted 
fever,   but   three  of   these  were   infected   from  lots  of  ticks 


ROCKY    MOUNTAIN    SPOTTED    FEVER.  55 

which  came  from  one  mountain  goat.  It  is  of  great  interest 
to  know  that  a  guinea-pig  inoculated  with  one  cubic  centi- 
meter of  blood  from  this  goat  did  not  develop  the  disease 
and  proved  susceptible  to  a  subsequent  inoculation  of  the 
virus  from  another  guinea-pig.  The  other  three  guinea-pigs 
were  infected  by  wild  ticks  collected  from  vegetation.  Two 
guinea-pigs  upon  which  ticks  fed  that  came  from  two  other 
goats,  while  they  did  not  show  symptoms  of  the  disease, 
proved  to  be  immune  to  subsequent  inoculation,  which  is 
presumptive  evidence  that  they  had  harbored  infective  ticks, 
thus  bringing  the  total  of  positive  results  in  McClintic's 
experiments  to  eight  from  ticks  from  six  difTerent  sources. 

In  all  of  the  above  experiments  by  Ricketts,  Maver  and 
McClintic,  substantially  the  same  technic  was  employed. 
Guinea-pigs  which  developed  no  evidence  of  the  disease  were 
tested  for  immunity  before  they  were  recorded  as  negative. 
Guinea-pigs  which  developed  the  disease  were  used  to  in- 
oculate other  guinea-pigs  in  order  to  prove  the  infection 
to  be  that  of  spotted  fever. 

R.  A.  Cooley^  also  records  the  infection  of  a  guinea-pig 
with  ticks  which  were  collected  by  W.  V.  King  in  the  Bitter 
Root  Valley.  In  this  experiment  one  of  four  guinea-pigs 
upon  which  one  hundred  and  sixty  ticks  fed  became  infected. 

VIII.      HISTORY  AND  IDENTITY  OF  THE  STRAINS  OF  VIRUS  USED. 

I.  Record.  —  Strain  I.  was  started  in  January,  191 6,  from 
ticks  sent  by  Surgeon  L.  D.  Fricks.  Two  guinea-pigs  were 
infected  by  a  male  and  female  tick  respectively,  and  the 
strain  obtained  from  the  female  tick  was  maintained  until 
August  23,  191 8.  The  various  transfers  are  shown  on  Chart 
No.  I.  These  ticks  were  infected  during  the  summer  of 
1915  on  guinea-pigs.  The  original  strain  was  recovered  three 
years  previously  by  Dr.  Fricks,  and  had  been  maintained 
wholly  in  guinea-pigs. 

Strain  II.  was  started  in  February,  191 6,  from  defibrinated 
blood  sent  by  Dr.  Fricks.  This  blood  came  from  a  guinea- 
pig  of  the  same  series  upon  which  the  ticks  used  to  start 


56 


WOLBACH. 


61//  N23 


Strain  \  .FromTicKs 


28 


A 


170 1 74 
Nl?/ 

59 


|8(]87|9/ 


Janulxj  1916  toyAagiLSt  19/6, 


5^o52 


77hpl3|% 


/»llll2 

?05[«3 
/07 


1-  I.  1-  rr 
67|7j|78|8ol6fc 

374/|55|6^ 


93//0 
^3|/'"i|"'l«i 


I2#33|/42|l45 

ne[r2s(r25|i37 

126 


?4|96l"'3      120     h'' 


l23|l32|l4l|f)^feop&||?58|i'(,5|/ 


/38 


)||27       |35m«|'s,j 
135      |l48 


'51160/63 


kl'i7 


Vfi  '7 

jSb|"3|8 

fol    A 


y  15  2-)  42. 

76l2o|4 


4 


3547 


Chart  i. 
Record  of  Strain  I.  —  The  numbers  refer  to  guinea-pigs.  Each  "  gener- 
ation "  occupies  a  vertical  column.  X  indicates  those  used  to  furnish 
blood  for  inoculation  of  the  guinea-pigs  recorded  in  the  next  column.. 
sj  indicates  those  studied  histologically  and  in  which  the  parasite  was. 
demonstrated. 

Strain  I.  were  fed,  and  the  only  difference  between  Strain  I. 
and  Strain  II.  was  that  the  former  had  been  passed  through 
ticks,  while  the  latter  had  been  maintained  by  continuous 
passage  through  guinea-pigs,  first  inoculated  from  the  human 
case.     The  record  of  Strain  II.  is  shown  in  Chart  No.  2. 

Another  strain  obtained  from  Surgeon  L.  D.  Fricks,  I  have 
called  the  Darby  strain,  because  the  source  was  a  case  which 
occurred  near  Darby,  Mont.,  near  the  head  of  the  Bitter  Root 
Valley.  The  ticks'were  fed  on  an  infected  guinea-pig  during 
the  summer  of  1915  by  Dr.  Fricks;  the  guinea-pigs  were 
infected  from  a'*  human  case  contracted  near  the  village  of 
Darby.  This  strain  was  maintained  by  me  for  a  compara- 
tively short  time*  from  a  guinea-pig  infected  by  a  tick  which 
was  numbered  XXVII  (Chart  3) .  Seven  of  these  original  ticks 
from  Dr.  Fricks,  two  males  and  five  females,  were  attached  to 
seven  different  guinea-pigs.  All  transmitted  the  disease. 
Type  examples  are  shown  in  the  protocols  on  page  91,  under 
"Adult  ticks  proved  to  be  infective." 


ROCKY   MOUNTAIN    SPOTTED   FEVER. 


57 


Defbrinatod  bUcdr'|3|''5l7|9 
from  Surg.  Fr;chs|zr4Ur8r/i: 


Strain  Z.    Fttruai 
15 


J     t.    SeyttmWr  V<)Ho. 


/9I22 

29 


» 
i»l«/ 


TIcKX  S«ri«6  .  TcKX  feA»"  Strain  2  Cpifs  33  &  34. 
Ju-ne  to  November  \9(6. 

125 


7(ckXQ-.P;^,2- 


4  7  rgp/h/s 
6 


^|/»|2J2t|3o|53fe«|^ 


34     13640 


l29l32|35        14/ 


/8  ai 


TitKXSr  Serlts.TickXSIfeAon   T.c^X  G^>!g    Z. 

Sep^ember|9lfcto^^a.^l9l7. 


_J/|3l"s|7|9J''lr3fe/8 


'io27 

A 

i/  22  <^ 

24 


3438 
35I39 
36 


33     |4/|f3|45l47k9|S/|53|55j57|59r6/|^3|65|?7|65|7(|'3|7s|77|79|fe|83l^ 


Chart  2. 
Record  of  Strain  II.  with  the  series  maintained  from  ticks  infected  from 
Strain  II.  —  The  numbers  refer  to  guinea-pigs.  Each  "generation" 
occupies  a  vertical  column.  X  indicates  those  used  to  furnish  blood  for 
inoculation  of  the  guinea-pigs  recorded  in  the  next  column.  ^  indicates 
those  studied  histologically  and  in  which  the  parasite  was  demonstrated. 


A  fourth  strain  was  started  in  November,  1917,  from  tv\-o 
guinea-pigs  sent  from  Washington  by  Surgeon  L.  D.  Fricks. 
This  strain  was  secured  in  the  summer  of  191 5  from  a  case 
in  Touro  County,  Cal.,  and,  according  to  Dr.  Fricks,  had 
been  passed  through  guinea-pigs  not  more  than  twenty-five 
times,  and  had  never  been  passed  through  ticks  in  the  labora- 
tory. This  strain  I  have  called  the  CaHfornia  strain,  and  a 
record  of  the  transfers  is  shown  in  Chart  No.  3. 

Hayes  strain.  —  This  strain  was  obtained  by  me  from  a 
case  contracted  on  O'Brien  Creek,  a  tributary  of  the  Bitter 
Root  River,  near  Missoula,  Mont.  Two  guinea-pigs  were 
inoculated  May  7,  1917,  each  with  5  c.c.  of  a  mixture  of 
equal  parts  of  blood  and  citrate  saline  solution,  twenty 
minutes  after  withdrawal  of  the  blood  from  the  patient. 

Record  of  temperatures:  Guinea  Pig  i.  —  May  7,  103;  May  8,  104.4; 
May  9,  102.2;  May  10,  103.4;  May  11,  105;  May  12,  103;  May  13,  105.8;. 
May  14,  105.6;   May  15,  102.4;   May  16,  dead. 


58 


WOLBACH. 


CaUfovma.    Strain.  l/ovemVicr  Wife  to  N^arch  \m. 


S<"-6  FricKs 


i 


s-Ui 


'r6\i9 


V  9 


27  V 

I^^Sel  3o\  32|  5i(l«|'j«|.jo|5o|4^f^<l49|f'te  ssli?!  »p  k3U5K7|^j 


Ub8Ny2?l^'iy35|-3»pr*'l«r« 


A' 


7/|74|7<[78|*> 


|57|w*|io3|wi|?o7|/o9]«/|7'3|*4'?lHK'feWi7|/M|l3l|fe^^ 


tf2 

rffslJfS  iSo|«2J  «»|/«|ff«|«S(l[/Aj|  'm 
(1l|;fflM>l'5)|r5<j(53J<5?|  1551/6/1/65/65 
MS 


/ 


Darby  Stram.  TTcKs  from  L.D-FricKs. 

■'  December  V9lb  t,  J«.«e  4917. 


QPii    lafecUJ    2 
by  Tick  XXVi/'  \3 


4, 
5    8| 

7 


?+|/e|2o|22l2l]l6|^8|!oI52|34|l6|§8|4o|42|4')iy48 
/shf|^lbEy|27|29|3(p3|S5i37l39|^M43|4Wl4? 


Chart  3. 
Record  of  California  strain  and  Darby  strain.  —  The  numbers  refer  to 
guinea-pigs.  Each  "  generation  "  occupies  a  vertical  column.  X  indicates 
those  used  to  furnish  blood  for  inoculation  of  the  guinea-pigs  recorded  in 
i;he  next  column.  V  indicates  those  studied  histologically  and  in  which 
"the  parasite  was  demonstrated. 


The  autopsy  showed  the  typical  lesions  of  Rocky  Mountain  spotted 
fever. 

Record  of  temperatures:  Guinea  Pig  2.  —  May  7,  103;  May  8,  103.6; 
May  9,  102.6;  May  10,  103.6;  May  11,  104.2;  May  12,  106;  May  13, 
104.2;   May  14,  dead. 

The  autopsy  showed  the  typical  lesions  of  Rocky  Mountain  spotted 
fever. 

Adult  unfed  ticks  furnished  by  Dr.  W.  V.  King,  secured 
by  dragging  in  the  vicinity  of  Florence,  Mont.,  were  fed  on 
Guinea-pig  i  between  May  14  and  16,  until  the  death  of  the 
guinea-pig.  The  strain  was  established  in  Boston  by  attaching 
two  female  ticks  and  one  male  tick  of  this  series  to  a  normal 
guinea-pig  on  June  2,  1917. 

Record  of  temperatures:  Hayes'  Guinea  Pig  3. — June  2,  no  tempera- 
ture; June  3,  no  temperature;  June  4,  100,  all  three  ticks  were  feeding; 
June  5,  101.6;  June  6,  loi;  June  7,  no  temperature;  June  8,  102. i;  June 
-9,  101.6;  June  ID,  no  temperature;  June  11,  103,  ticks  removed  almost 
fully  engorged;    June  12,  103.6;    June  13,  105. i. 

Guinea-pig  killed  on  June  13  for  inoculations.  Post-mortem  showed  the 
spleen  enlarged  to  double  its  size,  marked  injection  of  the  testes  and  polar 


ROCKY    MOUNTAIN    SPOTTED    FEVER. 


59 


fat  of  l)oth  testes  and  the  ingLiinal  nodes  enlarged  and  reddened.  Other 
tissues  of  the  body  were  negative.  Four  guinea-pigs  inoculated  from 
this  guinea-pig  ail  developed  the  disease  in  characteristic  form  on  the  fourth 
•day  after  inoculation.     A  record  of  these  transfers  is  shown  in  Chart  4. 


Hajes    Strain.Fir.t  Series.  A^l^.yHl7t.Aafu,t   1917. 


i 


Sjiotled  Feve 

Case  2. 

Hayes 


•6  r/c/rs^cdasi 


V  |r,cKsJ*3 

2. 


;(|'sl/iir2ikv 


9  32r333a'»o  40 
31       37 


8/2/6 
'5 1/31/7 


y 


Ha^es    Straxn,Au.guSt  1917  to  Septenxber  Wl6. 


I'ls|?7|!l9|5'|«|55fe7|?^6lfe3fes67  69^/^3  75^77  79  &183^asl87^&?92^W 
'fllw45^°P'^l«fetl58|&|l2k''kUl7obi|74l76|76N8zlSi|S6lfe8|9o9397|/»|r«^ 


^»T|'«|(Zl[fe3 
{ll&|u,|l24(M 


U(739|/3I 


..     J  rsollsJfel/sJ/JfJMW/lsslwlrrzWt 

"^Solp  r35  139 '■tS       _^    /3l|jV5|l57l'«t"llb3l/65|/»7|'«ll7/|l73|(7y 
[Hi  (36  /*!  HlMr^  152 

Chart  4. 
Record  of  Hayes  strain  established  from  Case  II.  and  reestablished  in 
guinea-pigs  from  ticks  infected  on  No.  19  of  the  original  series.  The  num- 
bers refer  to  guinea-pigs.  Each  "generation"  occupies  a  vertical  column. 
X  indicates  those  used  to  furnish  blood  for  inoculation  of  the  guinea-pigs 
recorded  in  the  next  column.  V  indicates  those  studied  histologically  and 
in  which  the  parasite  was  demonstrated. 


From  time  to  time  during  the  course  of  the  work  strains 
transmitted  from  the  above  by  ticks  were  maintained  in 
guinea-pigs  and  recorded  according  to  the  number  of  the 
tick.  For  example,  Tick  X.  strain  was  transmitted  by 
Tick  X.,  which  was  fed  on  Guinea-pigs  33  and  35  of  Strain  II. 
Tick  XVI.  strain  was  transmitted  by  Tick  XVI.,  which  was 
fed  on  Guinea  Pig  154  of  Strain  I.,  and  on  Guinea  Fig  2  of  the 
Tick  X.  strain.     These  records  are  shown  in  Charts  4  and  5. 

The  Hayes  strain  was  passed  through  ticks  a  number  of 
times;  for  example,  Guinea  Pig  44  of  this  strain  was  infected 
by  ticks  fed  as  nymphs  on  No.  19. 

Hayes  tick  strain,  August,  1918.  This  strain  was  estab- 
lished from  four  ticks  fed  as  nymphs  on  Guinea  Pig  19,  Hayes 
strain.  The  protocol  of  this  feeding  experiment  is  entered 
on  page  97,  under  "  Ticks  infected  as  nymphs,  some  of  which 
were  proved  to  be  infective."     Tick  A,   Hayes  strain,  was 


6o 


WOLBACH. 


established  by  feeding  nymphs  raised  from  eggs  deposited 
by  Tick  A  between  June  21  and  June  30,  1918.  The  larvae 
hatched  between  July  20  and  July  29,  1918.  They  were  fed, 
between  August  i  and  August  8,  on  a  normal  guinea-pig» 
They  molted  to  nymphs  between  August  19  and  August  23. 
The  nymphs  were  fed  on  Guinea  Pig  13,  Hayes  tick  strain  of 
August,  191 8,  September  18  to  September  26.  Some  of  the 
engorged  nymphs  molted  to  adults  between  October  22  and 
November  4.  The  strain  was  established  by  allowing  two 
male  ticks  of  this  series  to  feed  on  a  normal  guinea-pig 
December  19  to  December  24.  The  record  of  the  strain  is 
shown  in  Chart  5. 


4'ncKs   fed  as 


Hayes  S^ra\n    of  August  19(6  to  Decemfcer/9/6. 


Or-'iA'f'i 


z, 

3  7 


13 


32^ 

N37t3?|4/ 
35 


nfmnhs  on 


|77cKG.Pii|/ 

I   Hayes       fZ 


3  5  7    9// 
'2kr6r8|/o|/2 


Hayes  Stravu  of  D^cemVer  1918*;. 


Hayes  TicKlA" Strain,  December |«;f8E« 


nymphs  onC,.?ii*l3   TkM  A  Ci.P.f  /  p  5 PVP? 
Strain  of /\uj.l5l8.l       Hayes        r2l4r6|8|/o 


1/3    ./a 


i7P 


/j|24 


k|3T     fclw 


26130  33|35l4l  1+6 


^>fr\\  1 91  J; 


Chart  5. 
Record  of  Hayes  strain  tick  series  established  in  1918.  — The  numbers 
refer  to  guinea-pigs.  Each  "  generation  "  occupies  a  vertical  column. 
X  indicates  those  used  to  furnish  blood  for  inoculation  of  the  guinea-pigs 
recorded  in  the  next  column.  nI  indicates  those  studied  histologically 
and  in  which  the  parasite  was  demonstrated. 


2.  The  identity  of  the  strains  used.  —  The  above  strains 
of  the  virus  used  were  tested  at  different  times  in  order  to 
settle  any  doubt  as  to  their  identity.  As  Ricketts  showed, 
recovery  from  an  attack  of  spotted  fever  in  the  guinea-pig 
leaves  a  lasting  immunity.     I  have  frequently  verified  this> 


ROCKY    MOUNTAIN    SPOTTED    FEVER.  6 1 

and  assume  that  if  one  strain  confers  immunity  against 
another,  they  are  identical.  Ricketts'^  by  this  method 
showed  that  the  strains  of  virus  from  Idaho  and  Montana 
were  identical  in  nature. 

Strains  I.  and  II.  came  from  the  same  source,  as  noted 
above.  The  CaHfornia  and  Darby  strains  were  crossed  with 
Strain  II.  and  with  each  other  with  negative  results.  The 
Hayes  strain  was  crossed  with  Strain  II.  with  negative  results. 
Type  protocols  of  these  experiments  follow. 

The  immune  Strain  II.  guinea-pig  used  for  testing  with  the  California 
strain  was  infected  by  Tick  XIV.  Tick  XIV.  was  fed  on  Strain  II. 
Guinea  Pig  39,  July  12  to  15,  1916.  It  fed  August  2  to  7  on  a  normal 
guinea-pig  which  was  recorded  as  Tick  XIV.  guinea-pig  of  August  2. 

Record  of  Tick  XIV.  guinea-pig  of  August  2. 

Temperature  after  removal  of  tick:  August  7,  102.2;  August  8,  103; 
August  9,  104;  August  10,  106;  August  11,  106.1;  August  12,  105.8, 
scrotum  swollen  and  red;  August  13,  August  14,  105.2;  August  15,  105.2; 
August  16,  103.8;  August  17,  102.8;  August  18,  103,  scrotum  nearly 
normal,  the  site  of  the  tick  bite  is  markedly  indurated;  August  19,  102.8; 
August  20,  102.8;   August  27,  102;    September  2,  102. 

On  December  5  this  guinea-pig  was  inoculated  intraperitoneally  with 
I  cubic  centimeter  of  blood  in  citrate  saline  solution  from  California 
Guinea  Pig  3,  with  completely  negative  results,  as  shown  by  the  tempera- 
tures. 

December  5,  6,  102;  December  7,  102.4;  December  8,  101.4;  Decem- 
ber 9,  101.6;  December  10,  11,  101.2;  December  12,  101.6;  December 
13,  101.6;    December  14,  101.4;    December  15,  101.6;    December  16,  102. 

Result:  Immune  Tick  XIV.  (Chart  2)  guinea-pig  of  Strain 
II.  was  proved  immune  to  the  California  strain  from  California 
Guinea  Pig  3. 

Darby  strain  and  Strain  II.  (and  California  strain).  —  Tick  XIV. 
:guinea-pig  which  proved  immune  as  shown  above  the  California  strain 
was  inoculated  intraperitoneally  on  February  17,  1917,  with  .5  cubic  centi- 
meters of  blood  in  citrate  saline  from  Darby  strain  Guinea  Pig  13,  with 
completely  negative  results. 

Temperatures:  February  19,  loi;  February  20,  101.2;  February  21, 
101.4;  February  22,  101.8;  February  23,  101.2;  February  24,  loi; 
February  25,  26,  100.4.;   February  27,  loi. 

This  guinea-pig  lived  until  July  13,  1918,  and  presumably  died  of  old 
age. 

Result:  Immune  Tick  XIV.  guinea-pig  of  Strain  II.  and 
California  strain  was  proved  immune  to  the  Darby  strain. 


62  WOLBACH. 

Hayes  strain  and  Strain  II.  —  The  immune  guinea-pig  used  for  this 
test  was  No.  7  of  Tick  X.,  Strain  II.  (Chart  2).  This  sub-strain  was  trans- 
mitted by  Tick  X.  which  was  fed  on  Guinea  Pigs  34  and  35  of  Strain    II.. 

Temperature  of  Tick  X.  strain,  Guinea  Pig  7,  inoculated  from  No.  5, 
August  5,  1916.  August  5,  102.8;  August  8,  104.8;  August  9,  105; 
August  10,  105;  August  11:,  105.4;  August  12,  104;  August  13,  14,  105; 
August  15,  103;  August  16,  102.4;  August  17,  103;  August  18,  103; 
August  19,  103;  August  28,  103;  Septembers,  102. 

On  July  20,  1917,  eleven  and  a  half  months  later,  it  was  inoculated 
intraperitoneally  with  .5  cubic  centimeters  of  blood  in  citrate  saline  from 
Hayes  strain  Guinea  Pig  26. 

Temperatures:  July  20,  103;  July  21,  102;  July  22,  23,  loi;  July  24, 
100.6;    July  25,  lOO;    July  26,  102.4;    July  27,  100.6;    July  28,  loi. 

Result:  Immune  Tick  X.  Guinea  Pig  7  (Strain  II.)  was 
proved  immune  to  the  Hayes  strain. 

Conclusions:  As  Strains  I.  and  II.  were  identical  and 
guinea-pigs  immune  to  Strain  II.  were  also  immune  to  the 
Darby,  California  and  Hayes  strains,  and  guinea-pigs  immune 
to  the  California  strain  were  immune  to  the  Darby  strain,  we- 
may  conclude  that  the  viruses  of  these  strains  were  identical. 


IX.      THE   EXPERIMENTAL   TRANSMISSION    OF    ROCKY   MOUNTAIN 
SPOTTED    FEVER   BY   TICKS. 

I.  Transmission.- — Ricketts^"-  ^^'  ^^  and  his  associates 
showed  that  the  larvae  of  Dermacentor  venustiis  when  fed  upon 
infected  guinea-pigs  remained  infective  in  the  nymph  stage, 
and  that  nymphs,  when  infected,  remained  infective  after 
reaching  the  adult  stage.  He  also  showed  that  eggs  from  in- 
fected females  would  produce  the  disease  when  injected  into- 
guinea-pigs.  He  found  that  both  male  and  female  ticks 
would  transmit  the  disease.  Maver,^^  working  under  his  direc- 
tion, found  that  Dermacentor  marginatus,  from  Utah,  Am- 
hlyomma  americanum  linncBus  from  Missouri,  and  Dermacentor 
variabilis  from  Massachusetts  can  transmit  the  virus  of  Rocky 
Mountain  spotted  fever.  In  the  case  of  Dermacentor  venustusr 
Moore, ^^  working  under  the  direction  of  Ricketts,  found  that 
a  minimum  period  of  feeding  of  one  hour  and  forty-five 
minutes  was  required  to  infect  ticks  so  that  they  would  trans- 
mit the  disease.  The  average  time  was  about  ten  hours, 
while  he  states  in  his  conclusions  that  twenty  hours'  feeding: 


ROCKY   MOUNTAIN    SPOTTED    FEVER.  63 

was  almost  certain  to  infect  ticks.  The  minimum  incubation 
time  in  ticks  was  not  determined. 

This  phase  of  the  tick  transmission  problem  needs  further 
elucidation.  I  have  not  been  able  to  infect  adult  ticks  with 
the  same  ease.  Ricketts^^  stated  that  individual  ticks  \aried 
greatly  in  the  ease  with  which  they  could  be  made  infective 
by  feeding  on  infected  guinea-pigs.  He  records  ticks  which 
did  not  become  infected  by  a  single  feeding  for  periods  of 
eight  to  fourteen  hours,  and  he  also  expressed  the  opinion  that 
it  was  more  difficult  to  infect  male  ticks  than  female  ticks. 

My  own  results  have  borne  out  the  difficulty  of  infecting 
adult  ticks  in  intermittent  feedings.  The  minimum  time  of 
feeding  in  all  my  experiments  was  two  days.  It  M-as  frequently 
impossible  to  infect  a  tick  in  two  feedings  of  tv\^o  days  each, 
but  males  became  infective  as  easily  as  females.  Protocols  of 
experiments  in  tick  transmission  where  two  and  three  feedings 
were  required  are  entered  under  the  heading  of  "  Adult  ticks 
which  were  proved  to  be  infective."  In  fifteen  experiments 
I  have  made,  the  results  summarize  as  follows:  Four  were 
infective  after  a  single  feeding.  Two  were  infective  after  two 
successive  feedings.  Four  were  infective  after  two  feedings, 
having  failed  to  infect  guinea-pigs  in  a  test  following  the  first 
feeding.  One  required  three  feedings  to  make  it  infective, 
the  tests  after  the  first  and  second  feedings  having  proved 
negative.  Three  ticks  failed  to  become  infective  after  a 
single  feeding,  and  were  not  used  further.  One  tick  failed 
to  become  infective  after  two  feedings,  and  could  not  be  used 
again,  as  it  became  fully  engorged. 

The  minimum  incubation  period  in  the  tick  has  not  been 
determined.  The  shortest  time  after  a  single  feeding  in  my 
experiments  was  that  of  Tick  XL,  a  male,  which  was  fed 
July  28  to  July  30  on  an  infected  guinea-pig.  It  was  fed' 
August  2  to  August  7  on  a  normal  guinea-pig,  which  on 
August  7  had  a  temperature  of  106°  F.,  and  ran  a  typical' 
course  of  Rocky  Mountain  spotted  fever.  Making  an  allow- 
ance of  four  days  as  the  usual  incubation  period  in  the  guinea- 
pig,  the  incubation  period  in  the  tick  could  not  have  been 
more  than  six  days,  and  probably  not  more  than  five  days,  im 


■64.  WOLBACH. 

this  experiment.  The  length  of  time  that  the  virus  will  survive 
in  the  tick  has  not  yet  been  determined  fully.  The  longest 
period  of  my  experiments  was  that  in  the  case  of  ticks  infected 
-as  nymphs  between  July  2  and  July  11,  1917,  and  which  trans- 
mitted the  disease  as  adults  by  feeding  between  December  19 
and  24,  191 8,  a  period  of  seventeen  months.  The  protocol 
of  this  experiment  is  recorded  under  "  Ticks  infected  as 
nymphs,  some  of  which  were  proved  to  be  infective  in  the 
adult  stage." 

2.  The  care  and  feeding  of  ticks.  —  In  working  with  in- 
fected or  presumably  infected  ticks,  means  must  be  taken  for 
preventing  losses.  For  that  reason  a  careful  count  should  be 
made  each  time  the  containers  are  opened,  and  but  a  small 
number  of  ticks  kept  in  a  single  container.  The  most  con- 
venient containers  are  small  pill  boxes,  kept  inside  of  metal 
ointment  boxes.  The  latter  are  perforated  in  order  to  insure 
access  of  moisture,  which  is  of  great  importance  if  the  ticks 
are  to  be  kept  for  a  long  time.  An  excess  of  moisture  favors 
the  growth  of  molds,  which  is  usually  fatal  to  the  ticks.  I  have 
found  that  the  best  method  is  to  place  the  perforated  ointment 
boxes  containing  the  ticks  inside  an  air-tight  jar,  and  to 
supply  moisture  by  means  of  moist  filter  paper  or  cotton  kept 
out  of  contact  with  the  boxes. 

For  the  greatest  longevity  of  ticks,  storage  in  a  cold  room 
at  7°  C.  to  10°  C.  has  given  the  best  results.  At  this  low 
temperature  the  ticks  would  dessicate  rapidly  if  they  were  not 
kept  in  a  moist  atmosphere  inside  of  an  air-tight  receptacle. 

In  feeding  a  number  of  ticks  on  the  same  animal,  individual 
ticks  may  be  marked  by  amputating  the  tarsus  on  one  or  more 
legs.  The  feeding  of  individual  ticks  or  a  small  number  of 
ticks  may  be  easily  and  safely  done  by  placing  the  ticks  in  a 
small  wire  gauze  cage,  and  attaching  to  the  animal  by  means 
of  surgeons'  adhesive  plaster.  These  gauze  cages,  for  attach- 
ing to  guinea-pigs,  may  be  1.5  centimeter  to  2  centimeters 
in  diameter,  and  .5  centimeter  to  .8  centimeter  deep,  I  have 
made  them  in  the  shape  of  a  shallow  cylinder  with  a  flanged 
■edge,  like  a  man's  straw  hat,  in  order  that  they  may  be  sewed 


ROCKY    MOUNTAIN    SPOTTED    FEVER.  65 

to  the  non-adhesive  surface  of  adhesive  plaster.  After  the 
cages  are  sewn  to  the  adhesive  plaster,  a  circular  aperture  is 
cut  in  the  plaster  as  large  as  possible.  (Figs.  3  and  4.)  If 
the  ticks  are  violently  agitated  in  a  test  tube  before  introducing 
them  into  the  cage,  they  will  remain  stationary  for  a  brief 
period,  during  which  the  cage  can  be  applied  and  fastened 
to  the  shaved  abdomen  of  a  guinea-pig  or  other  animal. 
After  the  cage  is  attached  in  position,  a  swath  of  two-inch 
adhesive  plaster  is  wrapped  around  the  animal,  for  the  purpose 
of  more  securely  fastening  the  cage;  a  hole  should  be  cut  in 
the  adhesive  plaster  swath  large  enough  to  permit  the  cage 
to  project  through  it,  and  tight  enough  to  grasp  the  flange, 
and  keep  the  latter  applied  to  the  underlying  adhesive  plaster. 
(Fig.  5-) 

In  feeding  larvae  and  ticks  it  is  almost  impossible  to  keep 
count  of  the  numbers.  The  method  I  have  employed  was 
suggested  by  one  used  by  Surgeon  L.  D.  Fricks.  (Personal 
communication.)  The  uncounted  larvae  or  nymphs  are  intro- 
duced in  their  original  container  into  a  large  battery  jar  con- 
taining the  animal  upon  which  they  are  to  feed.  The  inner 
surface  of  the  jar  near  the  top  is  ringed  with  a  heavy  layer  of 
vaseline  one  or  two  centimeters  broad.  In  order  to  absorb 
■excreta  there  should  be  three  to  four  centimeters  of  clean 
white  sawdust  on  the  bottom  of  the  jar.  After  preparations 
are  made  for  covering  the  jar  with  a  fine-meshed  wire  gauze 
■or  tightly  woven  cloth,  the  containers  of  the  larvae  or  nymphs 
may  be  opened  by  means  of  long  forceps,  and  the  cover  quickly 
applied  and  made  tight  by  means  of  adhesive  plaster.  Food 
may  be  introduced  at  any  time  through  a  slit  which  may  be 
cut  in  the  cloth  or  gauze  top,  and  subsequently  sealed  with 
adhesive  plaster.  At  the  end  of  three  days  the  guinea-pig 
with  the  attached  ticks  should  be  quickly  transferred  to  a 
similarly  prepared  jar,  and  the  first  jar  placed  in  an  already 
heated  Arnold  sterilizer,  in  order  to  kill  the  ticks  which  have 
not  attached.  As  a  precaution  against  loss  by  ticks  dropping 
from  the  guinea-pig  while  the  transfer  is  being  made,  the 
manoeuver  should  be  accomplished  over  a  white  surface.  A 
bottle  of  xylol  or  benzol  should  be  at  hand  for  the  drenching 


66  WOLBACH. 

of  any  surface  suspected  to  harbor  escaped  nymphs  or  larvse. 
The  animal  is  allowed  to  remain  in  the  second  jar  until  the 
engorged  nymphs  or  larvae  have  dropped.  A  few  unengorged 
individuals  may  be  found  on  the  sides  of  the  jar  or  caught  in 
the  grease  ring.  The  animal,  after  removal,  should  be  im- 
mediately transferred  to  a  clean  glass  jar,  and  etherized,  when 
it  may  be  conveniently  searched  for  attached  ticks,  or  rendered 
innocuous  by  drenching  with  xylol  or  benzol.  The  engorged 
larvae  or  nymphs  can  be  detected  easily  in  the  sawdust,  which 
should  be  transferred  to  shallow  glass  dishes.  In  order  to 
handle  the  engorged  larvae  and  nymphs  without  injuring  them, 
I  have  employed  metal  forceps  with  thin  cardboard  extensions 
of  the  points,  making  it  possible  to  grasp  them  firmly  without 
crushing  them.  By  this  method  of  feeding  the  immature 
stages  of  the  ticks,  a  great  many  individuals  are  lost.  I  have 
been  able  to  recover  about  fifty  per  cent  of  those  introduced 
into  the  jars.     Its  advantage  is  safety. 

In  raising  ticks  from  eggs  I  have  usually  transferred  each 
engorged  and  impregnated  female  to  a  small  wide-mouth  glass 
bottle,  stoppered  with  cotton  covered  with  linen,  to  prevent 
the  larvae  from  becoming  entangled  in  the  cotton  fibers. 
During  the  period  preceding  and  during  ovipositation,  the 
female  should  be  kept  in  semi-darkness,  in  a  slightly  moist 
atmosphere.  After  the  eggs  are  deposited  the  dead  female 
should  be  removed  and  the  eggs  allowed  to  incubate  in  the 
original  receptacle,  whence,  after  hatching,  they  can  be  intro- 
duced into  a  jar  with  the  animal  upon  which  they  are  to  feed. 

3.  The  intermittent  feeding  of  adult  ticks.  - —  It  is  possible 
to  induce  an  adult  female  tick  to  feed  as  many  as  five  times 
at  fairly  widely  separated  intervals  (see  protocols  of  "Adult 
ticks  proved  to  be  infective,"  page  91).  It  is  important,, 
however,  that  the  ticks  should  be  detached  without  injuring 
the  mouth  parts,  and  this  can  be  done  only  with  certainty 
by  grasping  the  epidermis  of  the  animal  with  sharp-pointed 
stout  forceps  and  tearing  away  that  portion  to  which  the  tick 
is  attached.  The  procedure  can  be  done  best  with  the  aid 
of  prism  magnifying  binoculars,  as  manufactured  by  Zeiss 
or  Bausch  and  Lomb,  and  which  have  been  exceedingly  useful 
for  this  purpose. 


ROCKY   MOUNTAIN    SPOTTED    FEVER.  6/ 

X.      DISSECTION    AND    INTERNAL    ANATOMY    OF    TICKS. 

I.  The  dissection  of  ticks.  — A  binocular  dissecting  micro- 
scope with  erecting  prisms  is  an  absolute  essential.  The 
instruments  I  have  found  most  useful  are  small  kni\es  ground 
into  different  shapes,  made  from  cataract  and  iridectomy 
knives.  The  shaping  and  sharpening  should  be  done  under 
the  dissecting  microscope,  and  ^the  finest  jewelers'  oilstones 
used.  The  shapes  of  the  knives  I  have  found  most  useful 
are  shown  in  text-figure  i.     Mounted  needles  ground  with  a 


cutting  edge  can  be  made  quickly.  Fine  blunt-pointed 
mounted  needles  are  very  useful  for  removing  tracheee  and 
separating  organs.  Two  stout  yet  very  finely-pointed  forceps 
are  needed,  and  these  must  be  pointed  by  the  worker.  I  have 
found  it  advantageous  to  grind  the  points  as  fine  as  possible, 
sharper  than  ordinary  needles,  with  a  fairly  abrupt  taper  in 
order  to  get  correct  apposition  of  the  points  in  grasping 
objects. 

The  ticks,  in  rapid  work,  are  dissected  under  salt  solution 
(.8  per  cent  NaCl)  in  a  circular  trough  made  of  parafBn  and 
lampblack;  the  black  color  is  advantageous  for  the  contrast 
it  gives.  The  trough  should  be  molded  upon  a  glass  or  metal 
plate  which  can  be  clamped  to  the  microscope  stage. 

The  ticks  for'  dissection  are  fastened  by  pinning  to  the 
trough  with  a  fine  entomological  needle  passed  through  the 
body  at  the  base  of  the  capitulum.  The  first  cut  is  made 
completely  around  the  body  of  the  tick  through  the  integu- 
ment along  the  lateral  margins.  In  dissecting  partially  fed 
ticks  it  is  easy  to  make  this  cut  without  injuring  the  intestinal 
diverticulse  by  squeezing  the  margin  of  the  tick  with  a  fine- 
pointed  forceps,  which  displaces  the  viscera  at  that  point. 
The  knife  —  and  I  have  found  a  rigid  round-pointed  knife 


68  WOLBACH. 

with  a  very  keen  edge  shaped  like  A  (text-figure  i)  best  for 
this  purpose  —  is  passed  between  the  blades  of  the  forceps. 
The  cut  is  begun  at  the  posterior  border  and  then  extended 
anteriorly  on  each  side  until  the  camerostome  is  reached, 
each  extension  of  the  cut  being  made  between  or  close  to  the 
blades  of  the  forceps.  In  dissecting  engorged  ticks  much 
practice  is  required,  as  it  is  impossible  to  displace  the  viscera 
by  squeezing.  My  procedure  has  been  to  fasten  the  tick  in 
a  glass  trough  with  an  adhesive  mixture  of  beeswax,  pitch 
and  resin,  which  is  warmed  and  the  tick  pressed  into  it. 
It  has  been  advantageous  to  melt  the  mixture  with  a  hot  wire 
at  the  point  to  which  the  tick  is  to  be  fastened.  This  method 
assures  stability  of  the  tick  and  the  first  cut  can  then  be 
made  while  supporting  the  point  of  the  knife  against  a  needle 
or  forceps  held  close  to  the  side  of  the  tick.  After  the  cut 
along  the  margins  of  the  tick  is  finished,  if  fastened  by  a  pin, 
a  second  pin  should  be  passed  through  the  ventral  surface 
near  the  posterior  edge,  after  having  pushed  the  organs  away, 
in  order  to  keep  the  tick  in  position  while  removing  the  dorsal 
surface.  The  dorsal  surface  is  removed  by  grasping  the  rear 
end  with  the  forceps  and  with  a  round-bellied  knife  (A  or 
B,  text-figure  i),  carefully  scraping  away  the  hypoderm.  The 
base  of  the  capitulum  should  be  carefully  disarticulated  and 
left  attached  to  the  ventral  surface. 

With  sufficient  practice  it  is  possible  to  remove  the  dorsal 
surface,  leaving  the  organs  intact  and  enclosed  in  the  hypo- 
derm.  Portions  of  the  various  organs  may  now  be  removed 
for  smear  preparations,  after  incising  the  hypoderm,  by  grasp- 
ing with  the  forceps  and  cutting  with  the  fine  sharp-pointed 
knife  (C,  text-figure  i),  or  with  a  needle  with  a  cutting  edge. 

While  becoming  familiar  with  the  anatomy  of  the  tick,  the 
blunt-pointed  needles  are  useful  to  separate  the  organs  for  the 
purpose  of  identification. 

For  section  work  the  dissection  is  completed  by  detaching 
the  ventral  hypoderm  from  the  chitinous  integument,  best 
done  by  carefully  elevating  the  whole  with  a  blunt  needle 
at  the  posterior  border  and  gradually  working  forwards  by 


ROCKY    MOUNTAIN    SPOTTED    FEVER.  69 

lifting  and  scraping  against  the  integument  with  a  round- 
bellied  knife.  A  keen  edge  is  needed  in  cutting  through  the 
leg  muscles,  in  order  to  avoid  tearing  the  hypoderm.  After 
the  ventral  surface  of  the  organs  enclosed  by  hypoderm  has 
been  freed,  the  base  of  the  capitulum  is  disarticulated  from 
the  ventral  surface  and  left  attached  to  the  organs.  The 
capitulum  serves  as  a  convenient  handle  in  transferring  the 
organs  from  one  solution  into  another. 

A  pipette  fitted  with  a  rubber  teat  is  necessary  to  remove 
and  replenish  the  salt  solution  during  dissection  in  case  the 
intestinal  diverticular  are  ruptured,  as  the  contents  cloud 
the  solution.  The  pipette  is  also  useful  to  create  currents  in 
the  dissecting  solution  for  the  displacement  of  organs  while 
determining  relations. 

When  dissecting  for  anatomical  study  it  is  sometimes  advan- 
tageous to  replace  the  saline  solution  with  an  .8  per  cent  NaCl 
solution  containing  three  per  cent  commercial  formol.  This 
fluid  hardens  the  organs  and  makes  them  retain  their  shapes; 
it  also  makes  them  somewhat  tougher  and  less  liable  to  rupture. 

2.  Internal  anatomy  oi  Dermacentor  venustus  (Figs.  18  and 
19).  —  The  following  brief  description  of  the  gross  internal 
anatomy  of  Dermacentor  venustus  is  given  for  the  purpose  of 
making  the  text  references  to  the  various  organs  under- 
standable. 

The  internal  anatomy  of  the  different  genera  of  ticks  varies 
but  slightly,  so  that  the  descriptions  of  ticks  other  than 
Dermacentor  venustus  are  of  great  help,  and  the  reader  is 
referred  to  the  excellent  descriptions  in  Patton  and  Cragg's 
textbook,  and  to  the  articles  of  Samson,^"  Christophers^  and 
Robinson  and  Davidson^^;  the  last-named  paper  on  the 
anatomy  of  Argas  persicus  is  exceptionally  complete. 

After  reflection  of  the  dorsal  integument,  in  the  living  tick, 
the  heart  can  be  seen  beating  in  the  median  line,  over  the 
central  portion  of  the  alimentary  tract,  i.e.,  stomach  or  mid- 
intestine.  It  lies  just  anterior  to  the  middle  portion  of  the 
body  of  the  tick,  or  just  posterior  to  the  level  of  the  third 
coxa.     In    Dermacentor   venustus   it    appears    as    a    flattened 


70  WOLBACH. 

spheroid  with  four  lobulations.  Running  anteriorly  from  it 
is  the  main  blood  vessel,  or  aorta,  a  translucent  walled  tube 
of  considerable  strength,  which  passes  forward  in  the  median 
line,  descending  to  empty  into  the  periganglionic  sinus  just 
anterior  to  the  mid-intestine. 

The  dissection  of  the  alimentary  tract  is  best  accomplished 
by  carefully  freeing  the  salivary  glands,  and  removing  them 
from  the  body  cavity,  and  then  carefully  detaching  the 
tracheae  from  the  organs.  This  can  be  done  easily  if  the 
larger  tracheal  trunks  are  grasped  with  the  forceps  and,  while 
under  tension,  the  smaller  branches  are  combed  away  from 
the  organs  with  a  blunt-pointed  needle.  The  oesophagus  can 
be  seen  coming  from  the  pharynx,  and,  entering  the  brain 
anteriorly  on  the  ventral  side,  it  passes  backwards  and  emerges 
on  the  dorsal  surface  of  the  brain  near  the  posterior  margin, 
where  it  enters  the  mid-intestine  or  stomach.  The  mid- 
intestine  is  a  short  tubular  organ,  and,  together  with  the 
diverticulse,  is  thin-walled  and  transparent,  and  always  con- 
tains dark  brown  to  black  contents.  From  the  mid-intestine 
or  stomach  arise  the  diverticulse  and  hind  intestine  or  rectum. 
The  hind  intestine  arises  from  the  ventral  side  of  the  mid- 
intestine,  slightly  anterior  to  its  middle  portion,  and  descends 
ventrally  and  posteriorly  to  open  into  the  rectal  sac.  The 
rectal  sac,  in  its  partially  filled  state,  appears  opaque  whitish. 
It  presents  four  lobes,  two  anterior,  which  embrace  the  lower 
end  of  the  hind-intestine,  and  two  posterior  lobes,  which  are 
shorter  than  the  anterior,  and  embrace  the  anus.  The  anus 
arises  on  the  ventral  surface  of  the  posterior  margin  of  the 
Tectal  sac.  Opening  into  the  rectal  sac,  close  to  and  on  each 
side  of  the  median  line  on  its  ventral  surface,  near  the  junction 
with  the  hind-intestine  or  rectum,  are  the  two  Malpighian 
tubes. 

(a)  The  intestinal  diverticulse  (Fig.  i8).  —  The  anterior 
end  of  the  mid-intestine  divides  into  two  main  trunks,  a  right 
and  left  anterior  lateral  division,  each  of  which  gives  off  three 
branches;  an  anterior  diverticulum,  which  is  short  but  which 
reaches  to  the  anterior  end  of  the  body  on  the  dorsal  surface; 


ROCKY    MOUNTAIN    SPOTTED    FEVER.  7 1 

a  median  branch,  which  takes  a  slightly  tortuous  course  to 
the  anterior  end  of  the  body  on  the  dorsal  surface;  and  a 
posterior  branch,  which  is  much  the  larger  of  the  three. 
This  posterior  branch  divides  soon  after  its  origin  at  about 
the  level  of  the  third  coxa,  into  two  secondary  branches,  an 
external  branch,  which  turns  backward  and  forward  and  then 
upwards  near  the  lateral  margin  of  the  body,  and  an  internal 
branch  which  gives  off  a  tertiary  branch  at  the  level  of  the 
posterior  margin  of  the  fourth  coxa.  The  tertiary  branch 
descends  and  then  runs  anteriorly  close  to  the  lateral  margin 
of  the  body  along  the  ventral  surface  to  a  point  between  the 
first  and  second  coxae.  The  main  internal  (secondary)  branch 
is  continued  backwards  along  the  dorsal  surface  to  the  pos- 
terior lateral  margin,  descends  to  the  ventral  surface,  and  is 
then  directed  anteriorly  and  inwards,  almost  reaching  the 
median  line.  It  terminates  just  anterior  to  the  brain,  and 
lies  in  contact  with  the  lateral  surface  of  the  brain;  its  tip 
may  curve  inwards  so  as  to  embrace  the  anterior  surface  of 
the  brain.  This  branch  is  one  of  the  largest  of  the  intestinal 
diverticulae. 

The  posterior  end  of  the  mid-intestine  or  stomach  divides 
into  a  right  and  a  left  posterior  lateral  division,  each  of  which 
in  turn  divides  into  two  branches,  a  lateral  and  a  median 
branch,  both  of  large  size.  The  lateral  branch  curves  out- 
ward and  backwards  on  the  dorsal  surface,  descends  to  the 
ventral  surface  at  the  posterior  margin  of  the  tick,  and  curves 
forward  to  terminate  somewhere  between  the  posterior  mar- 
gin and  the  rectal  sac.  It  usually  terminates  on  the  dorsal 
surface  of  the  rectal  sac,  but  may  terminate  at  the  posterior 
margin.  The  median  branch  passes  backwards,  descends  to 
the  ventral  surface  at  the  posterior  margin  of  the  body  and 
extends  on  the  ventral  surface  of  the  body  close  to  the  median 
line  to  the  anterior  end,  ventral  to  all  organs,  and  in  contact 
with  the  uterus.  Its  blind  ending  is  usually  found  just 
anterior  to  the  brain. 

(b)  The  Malpighian  tubes.  —  The  Malpighian  tubes  in  the 
dorsal  dissection  appear  on  each  side  as  delicate  tubes  with 
opaque   white   contents    near   the   median   line.     Each    tube 


72  WOLBACH. 

forms  a  sharply  flexed  loop  near  the  median  line  dorsal  to 
and  at  the  level  of  the  anterior  lateral  divisions  of  the  ali- 
mentary tract.  The  two  arms  of  this  loop  at  first  lie  in 
close  contact  (7  in  Fig.  18).  Their  course  is  tortuous,  and 
posteriorly  they  separate,  one  disappearing  between  the  median 
and  lateral  branches  of  the  posterior  lateral  division  of  the 
alimentary  tract,  the  other  external  to  the  lateral  branch  of 
this  division,  and  internal  to  the  internal  (secondary)  branch 
of  the  posterior  branch  of  the  antero-lateral  division  of  the 
alimentary  tract.  The  course  of  the  Malpighian  tubes  is 
best  studied  from  a  ventral  dissection.  Each  takes  origin 
on  the  ventral  surface  of  the  body,  lateral  to  and  anterior  to 
the  brain,  near  the  posterior  margin  of  the  basis  capituli. 
It  passes  outwards  and  backwards  near  the  ventral  surface 
through  the  divisions  of  the  salivary  glands,  where  it  makes 
a  number  of  turns,  again  passing  posteriorly  and  coiling 
around  the  main  tracheal  trunks.  It  then  passes  to  the 
dorsal  surface  of  the  body,  between  the  lateral  branch  of  the 
posterior  lateral  division  and  the  internal  secondary  branch 
of  the  posterior  (third)  branch  of  the  antero-lateral  division, 
and  goes  forward  to  form  the  loop  already  described.  The 
distal  arm  turns  posteriorly  to  disappear  between  the  median 
and  lateral  branches  of  the  posterior  lateral  division  of  the 
alimentary  tract,  whence  it  passes  to  the  ventral  surface  of 
the  body,  travels  anteriorly  to  reach  a  point  at  about  the 
junction  of  hind-intestine  and  mid-intestine,  and  finally  back- 
wards to  terminate  in  the  rectal  sac  (Fig.  19).  In  its  course 
the  Malpighian  tube  lies  in  contact  with  every  organ  in  the 
body,  parallels  the  ovary  for  a  considerable  distance,  and  in 
its  distal  portion  lies  in  contact  with  the  oviducts. 

(c)  The  salivary  glands.  —  The  salivary  glands  are  recog- 
nizable with  ease  because  of  their  characteristic  appearance, 
which  is  very  much  like  that  of  a  bunch  of  grapes.  They 
have  a  porcelain-white  appearance,  and  lie  on  each  side  of 
the  body  over  the  bases  of  all  four  legs.  They  lie  in  contact 
internally  with  the  uterus,  oviducts  and  ovaries,  dorsally  and 
ventrally  with  the  coils  of  the  intestinal  diverticulae.     They 


ROCKY    MOUNTAIN    SPOTTED    FEVER.  73 

are  traversed  by  the  Malpighian  tubes.  The  main  duct  of 
the  saHvary  gland,  considering  the  size  of  the  organ,  is  very 
small,  but  can  readily  be  found  as  a  transparent  tube  entering 
the  pharynx. 

{d)  The  female  reproductive  system  (Fig.  19).  —  This 
description  is  from  a  partially  fed,  unimpregnated  female. 
In  the  dorsal  dissection  of  the  tick,  the  ovary  is  easily  recog- 
nized as  a  translucent  whitish  organ  studded  with  ova  running 
transversely  across  the  dorsum  of  the  rectal  sac,  but  ventrally 
to  the  origin  of  the  posterior  intestinal  diverticulae.  From 
this  point  it  can  be  traced  forwards  and  upwards,  along  a 
tortuous  course,  to  the  anterior  half  of  the  body,  where  it 
becomes  continuous  with  the  small  calibered  oviduct.  The 
oviduct  passes  forwards  and  inwards  to  make  a  loop  near  the 
vagina.  The  returning  arm  passes  backw'ards  again  and 
forms  a  loop  near  the  junction  of  the  oviduct  and  ovary. 
The  distal  arm  returns  in  contact  with  the  other  two  arms 
and  joins  the  oviduct  on  the  opposite  side  to  form  the  sac- 
culated uterus.  The  three  arms  forming  these  loops  of  the 
oviduct  lie  in  close  contact  and  in  a  horizontal  plane.  The 
vagina  is  a  relatively  large  organ  which  passes  ventrally  and 
anteriorly  to  open  into  the  genital  aperture.  On  the  dorsal 
surface  of  the  vagina  are  two  tubular  glands,  one  on  each 
side  —  the  accessory  glands. 

(e)  The  brain  (3  in  Fig.  19).  —  The  brain  is  a  relatively 
small  white  organ,  in  shape  a  flattened  spheroid,  with  the 
posterior  margin  slightly  truncated.  It  lies  in  the  triangle 
formed  by  the  bifurcation  of  the  intestinal  tract  posteriorly 
and  the  salivary  glands  on  each  side,  approximately  at  the 
level  of  the  second  coxa.  It  gives  off  nerve  trunks  of  rela- 
tively large  size,  the  distribution  of  which  has  been  determined 
for  other  ticks,  particularly  Argas  persicus.  One  can  recog- 
nize in  Dermacentor  venustus  the  posterior  branches,  so-called 
"  splanchnic  "  nerves,  four  lateral  branches,  going  to  the  four 
legs,  and  delicate  branches  going  anteriorly,  two  on  each  side 
of  the  median  line,  and  presumably  corresponding  to  thepalpal 
and  mandibular  nerves  of  Argas. 


74  WOLBACH. 

(/)  The  male  reproductive  organs.  —  The  testis  occupies 
practically  the  same  position  as  the  ovary  in  the  female, 
and  in  the  mature  tick  {D.  venustus)  occupies  a  large  part 
of  the  body  cavity.  Posteriorly  it  forms  several  large  loops 
on  each  side  between  the  loops  of  intestinal  diverticulae. 
Anteriorly  the  testis  on  each  side  tapers  gradually  to  pass 
into  the  much  smaller  calibered  vas  deferens,  which  makes 
several  loops  at  about  the  level  of  the  genital  aperture,  on 
each  side  of  the  ejaculatory  duct.  The  distal  arm  of  the 
loop  finally  passes  posteriorly  and  ventrally  between  the  coils 
of  the  accessory  glands  to  form  another  loop,  and  turning 
forward  becomes  much  increased  in  caliber.  The  dilated 
terminal  ends  of  the  vasa  deferentia  lie  in  contact,  side  by 
side,  entirely  surrounded  by  the  accessory  glands;  they  ter- 
minate anteriorly  in  the  seminal  vesicle  which  lies  in  a  position 
corresponding  to  the  uterus  in  the  female,  and  is  also  concealed 
from  all  sides  by  the  accessory  glands.  Anteriorly  and  in- 
feriorly  the  seminal  vesicle  is  continued  into  the  ejaculatory 
duct  which  communicates  with  the  genital  aperture  correspond- 
ing to  the  vagina  in  the  female. 

The  accessory  gland  forms  a  complex  arrangement  of  curved 
tubes  of  large  size,  bilaterally  symmetrical,  opening  into  the 
ejaculatory  duct.  In  D.  venustus,  opening  directly  into  the 
ejaculatory  duct,  are  two  short,  opaque,  white  glands  on  each 
side,  a  pair  anterior  and  ventral  in  relation  to  a  pair  which 
lie  immediately  dorsal  and  posterior.  The  remaining  lobes 
which  form  the  bulk  of  the  mass  of  accessory  glands  are  three 
in  number  on  each  side,  and  take  origin  from  an  unpaired 
median  structure  which  passes  backwards  and  then  upwards 
and  forwards,  encircling  the  proximal  end  of  the  ejaculatory 
duct  and  terminates  in  two  short  arms  which  lie  dorsal  to 
the  seminal  vesicle.  This  median  lobe  on  the  ventral  side 
is  of  small  caliber,  where  it  turns  upwards  and  forwards;  it 
becomes  of  large  size  and  gives  off  four  sacs,  two  on  each  side; 
the  first  pair  at  the  point  of  flexure  are  the  larger,  the  second 
pair  are  immediately  anterior  to  the  first  or  at  the  beginning 
of  the  dorsal  arm  of  this  median  lobe.  Between  these  sac- 
culations and  the  bicornuate  end  the  lobe  presents  a  fusiform 


ROCKY    MOUNTAIN    SPOTTED    FEVER.  75 

shape.  The  lateral  lobes  arising  from  this  median  lobe  all 
take  origin  from  the  ventral  or  proximal  arm,  all  close  together 
and  near  the  ejaculatory  duct.  The  first  pair  of  lobes  are  of 
large  size  and  each  divides  into  two  arms  which  pass  dorsally 
and  meet  their  fellows  in  the  median  line  above  the  dorsal 
arm  of  the  median  lobe.  The  second  pair  are  short,  thick 
lobes  which  lie  on  each  side  of  the  ventral  arm  of  the  median 
lobe.  The  third  pair  are  long,  slender  lobes  which  extend 
backwards,  parallel  to  the  median  line  and  terminate  close 
to  the  posterior  margin  of  the  body. 


XI.      TECHNIC. 

1.  The  formula  for  the  Giemsa  stain  used  is:  Azur  II.  eosin 
(Gruebler),  3  grams;  Azur  II.  (Gruebler),  .8  grams;  Merck's 
reagent  methyl  alcohol,  375  grams;  Merck's  reagent  glycerine, 
125  grams. 

2.  Technic  of  making  smear  preparations  from  ticks  and 
animals.  —  In  making  preparations  from  the  tick  organs  it 
is  advisable  to  tease  the  tissue  apart  with  very  sharp  needles 
under  the  dissecting  microscope  in  a  drop  of  .8  per  cent  salt 
solution,  rather  than  to  crush  the  tissues.  Whereas  the  micro- 
organisms are  easily  demonstrable  in  cells  or  fragments  of 
cells,  they  are  found  with  considerable  difficulty  outside  of 
these  situations,  and  for  this  reason  I  have  even  entertained 
the  hypothesis  that  the  microorganisms  possess  great  fragility. 
The  preparations  made  in  this  manner  are  air  dried,  fixed 
in  absolute  alcohol  for  fifteen  to  twenty  minutes,  and  stained 
in  Giemsa's  stain  diluted  in  proportions  of  one  drop  to  one 
cubic  centimeter  of  distilled  water.  The  preparations  should 
be  allowed  to  stain  for  two  to  four  hours. 

For  the  demonstration  of  the  parasites  in  smear  preparations 
from  animal  tissues,  much  patience  is  required  in  order  to 
obtain  suitable  material.  It  is  useless  to  look  for  the  organ- 
isms in  preparations  made  by  crushing  tissues  from  any 
source.  I  have  found  them  only  in  preparations  made  from 
the    cutaneous    and    subcutaneous    tissues    in    monkeys    and 


76  WOLBACH. 

guinea-pigs,  and  the  tendon  sheaths  in  guinea-pigs.  As  they 
are  situated  almost  exclusively  in  the  walls  of  the  blood 
vessels,  it  is  necessary  to  disintegrate  these  structures,  and 
this  I  have  accomplished  by  putting  the  tissue  upon  the 
stretch  and  patiently  scraping  with  a  very  sharp  razor  held 
vertically  and  passed  across  the  tissues  with  an  oblique  sliding 
motion.  If  the  under  surface  of  the  skin  from  the  scrotum 
of  infected  guinea-pigs  and  monkeys  is  treated  in  this  way^ 
and  the  material  accumulating  on  the  razor  edge  be  carefully 
separated  and  fixed  upon  slides,  it  is  usually  possible  to 
obtain  cells  containing  the  organisms.  As  in  the  case  of 
smear  preparations  from  ticks,  organisms  outside  of  cells  are 
almost  impossible  to  find,  even  though  the  preparations  are 
made  from  regions  proved  by  sections  to  contain  them  in 
large  numbers. 

In  smear  preparations,  as  in  sections,  the  parasite  of  Rocky 
Mountain  spotted  fever  decolorizes  by  Gram's  method.  It 
is  difficult  to  stain  with  ordinary  aniline  dyes,  and  only 
Giemsa's  stain  has  given  good  results. 

3.  Histological  technic.  —  Tick  tissues  and  mammalian 
tissues  have  been  treated  alike  during  the  latter  half  of  this 
work.  The  method  employed  with  best  results  is  a  modifica- 
tion of  Giemsa's  stain.  The  tissue  is  fixed  in  Zenker's  fluid 
thoroughly  saturated  with  corrosive  sublimate,  and  preferably 
without  the  addition  of  acetic  acid.  After  embedding  in 
paraffin  and  sectioning,  slides  are  treated  in  the  usual  way, 
except  that  an  extra  step  is  taken  to  insure  complete  removal 
of  the  iodin,  which  is  employed  to  remove  crystals  of  cor- 
rosive sublimate  deposited  in  the  tissues.  Before  placing  in 
water  the  sections  are  treated  with  a  half  per  cent  sodium 
hyposulphite  solution  for  ten  or  fifteen  minutes,  and  then 
thoroughly  washed  in  running  water  followed  by  distilled 
water.  The  slides  are  stained  in  a  slightly  alkaline  mixture. 
For  the  best  results  it  is  essential  to  start  with  distilled  water 
free  from  traces  of  acid,  or  to  determine  by  trial  the  amount 
of  alkali  required  for  the  best  results.  Starting  with  the 
neutral  distilled  water,  I  have  found  that  two  to  four  drops 


ROCKY   MOUNTAIN    SPOTTED    FEVER.  77 

of  a  half  per  cent  sodium  bicarbonate  solution  to  one  hundred 
cubic  centimeters  of  water  gives  the  required  alkalinity.  I 
have  also  found  it  advantageous  to  retard  the  precipitation 
of  the  dye,  and  for  that  purpose  add  three  to  four  cubic  centi- 
meters of  reagent  methyl  alcohol  to  each  one  hundred  cubic 
centimeters  of  water.  The  formula  for  the  stain  which  has 
given  the  most  uniformly  good  results  is:  Distilled  water, 
lOO  cubic  centimeters;  .5  .per  cent  sodium  bicarbonate,  2  to  4 
drops;  reagent  methyl  alcohol,  3  cubic  centimeters;  Giemsa's 
stain,  2.5  cubic  centimeters. 

The  stain  should  be  poured  over  the  slides  immediately 
after  mixing,  and  should  be  changed  twice  during  the  first 
hour,  and  allowed  to  remain  in  the  third  solution  for  twelve 
to  eighteen  hours.  The  slides,  which  are  heavily  overstained 
by  this  method,  are  differentiated  in  ninety-five  per  cent  ethyl 
alcohol.  The  procedure  of  differentiation  really  consists  in 
removing  the  excess  of  stain  to  a  point  where  good  histological 
detail  is  secured.  If  the  sections  are  too  blue,  a  better  balance 
may  be  secured  by  adding  very  small  quantities  of  colophonium 
to  the  alcohol.  After  differentiation  the  sections  should  be 
rapidly  dehydrated  in  absolute  alcohol,  cleared  in  xylol  and 
mounted  in  oil  of  cedarwood. 

The  various  steps  in  the  technic  are  as  follows: 

1.  Fix  in  Zenker's  fluid  (formula:  corrosive  sublimate, 
■6  grams,  potassium  bichromate  2.5  grams).  Twenty-four 
hours  should  be  allowed  for  animal  tissues,  but  two  to  six 
hours  for  tick  tissues  is  sufficient. 

2.  Embed  in  paraffin  and  section  at  S/jl  or  less. 

3.  Xylol,  alcohol,  Lugol's  solution;   alcohol  as  usual. 

4.  .5  per  cent  sodium  hyposulphite  to  remove  the  last  traces 
of  iodin,  ten  to  fifteen  minutes. 

5.  Wash  in  running  water  ten  minutes,  followed  by  distilled 
water. 

6.  Stain,  differentiate,  dehydrate  and  clear  as  above,  and 
mount  in  oil  of  cedarwood. 

The  staining  of  paraffin  sections  by  Giemsa's  stain  is  no 
more  complicated  or  difficult  than  using  the  eosin-methylene 
blue  stain.     One  condition,  however,  is  absolutely  essential. 


78  WOLBACH. 

and  that  is  that  the  sections  should  be  thin,  not  over  five 
microns. 

Other  methods  may  be  used  for  the  demonstration  of  the 
parasite.  The  eosin,  methylene-blue  stain  will  occasionally 
produce  excellent  results,  but  gives  less  clear  pictures.  A 
very  satisfactory  method,  which  of  course  does  not  suffice 
for  histological  study,  is  to  overstain  with  Loefifler's  methylene- 
blue;  for  example,  one  or  two  hours  in  the  paraffin  oven  at 
55°  C.  and  then  differentiate  in  i  to  looo  or  i  to  2000  acetic 
acid  in  water.  After  washing  in  distilled  water,  the  sections 
should  be  transferred  immediately  to  absolute  alcohol,  cleared 
in  xylol  and  mounted  in  balsam.  The  stain  recently  devised 
by  Goodpasture^^  for  demonstration  of  the  influenza  bacillus 
in  tissues  gives  fair  results,  although  confusing  because  of  the 
intense  staining  of  other  material  occurring  in  the  lesions. 
On  the  whole,  Giemsa's  stain  has  proved  much  the  more 
satisfactory.  It  is  of  interest  to  note  that  when  applied  after 
fixation  in  Schaudin's  fixative,  as  originally  recommended  by 
Giemsa,  it  is  almost  impossible  to  demonstrate  the  parasites. 
On  the  other  hand,  very  excellent  results  have  been  occasion- 
ally secured  after  this  fixation  by  the  eosin-methylene-blue 
stain. 


XII.       THE    PARASITE. 

I.  The  parasite  in  mammals.  —  Early  in  the  investigation 
of  Rocky  Mountain  spotted  fever  in  guinea-pigs  the  conclusion 
was  arrived  at  that  the  nature  of  the  lesion  in  the  blood 
vessels  demanded  the  local  presence  of  a  parasite.  Le  Count^° 
was  of  the  same  opinion  while  making  his  studies  on  the 
pathological  anatomy  of  spotted  fever. 

The  first  discovery  of  the  parasite  was  made  with  the  eosin- 
methylene-blue  stain  in  thin  paraffin  sections  of  Zenker-fixed 
material.  It  was  a  surprise  to  find  that  Giemsa's  stain  used 
with  tissues  fixed  in  Schaudin's  fixative  (two  parts  saturated 
corrosive  sublimate,  one  part  absolute  alcohol)  would  not 
demonstrate  this  organism  at  all  satisfactorily,  although  giving 
most  excellent  results  with  trypanosomes  and  relapsing  fever 


ROCKY    MOUNTAIN    SPOTTED   FEVER.  79 

spirochsetes  in  contra!  tissues.  In  the  course  of  experiments 
with  this  stain  it  was  found  that  the  ordinary  staining  efifect 
could  be  reversed  if  the  tissues  were  fixed  in  Zenker's  fixative, 
and  differentiated  with  ethyl  alcohol.  By  reversal  of  the  stain 
is  meant  the  staining  of  chromatin  blue  and  cytoplasm  pink, 
whereas  in  successful  preparations  stained  after  fixation  in 
Schaudin's  fixative,  the  cytoplasm  is  blue  and  the  chromatin 
red  or  purple  red,  as  in  smear  preparations.  The  presence 
of  the  chrome  salt  in  the  fixative  seems  to  be  requisite  for 
the  uniformly  successful  demonstration  of  the  spotted  fever 
parasite.  A  number  of  methods  using  alkaline  methylene-blue 
as  the  principal  staining  agent  which  were  successful  with 
Zenker-fixed  tissues  were  unsuccessful  in  tissues  fixed  in 
alcohol  and  formalin,  although  occasionally  giving  very  fair 
results  with  tissues  fixed  in  saturated  corrosive  sublimate. 
In  the  description  of  the  parasite  it  is  necessary  to  consider 
the  various  appearances  found  in  mammalian  tissues  and 
in  tick  tissues.  It  is  much  easier  to  demonstrate  parasites 
both  in  ticks  and  mammalian  tissues  in  sections  than  in 
smears,  a  fact  which  is  considered  elsewhere  in  this  report. 
The  morphology  and  distribution  in  mammalian  tissues  are 
identical  in  all  types  studied,  —  man,  monkey,  rabbit  and 
guinea-pig.  White  rats  and  mice  were  found  not  to  be 
susceptible. 

In  sections  (Figs.  44,  46,  48,  50  and  63  to  68)  the  parasite 
invariably  has  the  form  of  a  minute  paired  organism,  often 
surrounded  by  a  very  narrow  but  definite  clear  zone  or  halo, 
as  if  encapsulated.  It  is  very  often  possible  to  show  that  the 
distal  ends  of  the  pairs  are  tapered,  so  that  the  appearance 
may  be  likened  to  that  of  a  diminutive  pair  of  pneumococci. 
This  paired  lanceolate  form  is  found  in  the  endothelial  cells 
of  the  vascular  lesions  (Fig.  50),  and  most  abundantly  in 
smooth  muscle  cells  of  the  media  of  vessels  with  the  lesions; 
and  individual  smooth  muscle  fibers  are  frequently  found 
completely  filled  with  them  (Figs.  48,  64,  66,  68  and  69). 
Rarely  the  parasite  is  found  in  endothelial  cells  detached 
from  the  vessel  walls  but  usually  incorporated  in  thrombi. 


:80  WOLBACH. 

They  have  also  been  found  outside  of  blood  vessels,  in  en- 
dothelial cells,  which  collect  in  and  around  the  adventitia. 
These  lanceolate  forms  in  mammalian  tissue  are  very  uniform 
in  size,  as  seen  in  sections.  The  length  of  a  pair  ranges  from 
slightly  under  to  slightly  over  one  micron,  the  width  is  cer- 
tainly not  over  one  quarter  of  the  length  of  the  pair,  and 
probably  lies  between  .2  and  .3  micron.  Rarely  in  smooth 
muscle  cells  a  smaller  form  is  found,  closely  packed,  in  great 
numbers,  comparable  in  size  to  the  intranuclear  forms  in  ticks. 

In  smear  preparations  of  mammalian  tissues  made  by  the 
method  described  elsewhere  in  this  report,  one  finds  in  addi- 
tion to  the  lanceolate  forms,  slender  rod-shaped  forms,  some 
•of  which  exhibit  polar  granules  (Fig.  29).  With  the  Giemsa 
stain  applied  after  ethyl  alcohol  fixation,  these  slender  rods 
-stain  delicately  pale  blue  in  color.  The  polar  granules  stain 
purplish  or  reddish.  The  sharpness  of  outline  usually  seen 
with  bacteria,  accidentally  or  intentionally  introduced  into 
the  preparations,  is  a  marked  contrast  to  the  rather  vaguely 
■defined  outlines  of  the  spotted  fever  organisms.  These  rod- 
Jike  forms  often  occur  in  pairs,  the  individuals  of  which  may 
be  almost  a  micron  in  length.  In  addition  to  the  rods  and 
lanceolate  forms  in  these  smears,  there  are  very  minute  pale- 
blue  staining  rounded  forms.  These  rods  and  minute  rounded 
forms  resemble  the  first  forms  of  the  parasite  which  occur 
in  smear  preparations  in  the  intestinal  tract  of  infected  ticks. 

The  demonstration  of  the  parasites  in  the  circulating  blood 
is  extremely  difficult.  Ricketts  unquestionably  saw  this  or- 
ganism in  the  blood  of  man  and  guinea-pigs,  and  he  described 
it  as  "  having  the  form  of  two  somewhat  lanceolate  chromatin- 
staining  bodies  separated  by  a  slight  amount  of  eosin-staining 
substance  "  — a  description  which  was  based  on  preparations 
of  blood  stained  by  Giesma's  stain  as  furnished  by  Gruebler. 
With  the  Giemsa  stain  I  have  been  using,  the  lanceolate  bodies 
in  blood  films  stain  reddish  or  purple,  and  are  separated  by  a 
very  slight  amount  of  bluish-staining  material.  In  thick  film 
preparations,  in  which  the  dried  drop  of  blood  is  treated  with 
distilled  water  before  fixation  in  absolute  alcohol,  the  lanceo- 
late or  oval  paired  forms  often  appear  to  be  surrounded  with 


ROCKY   MOUNTAIN    SPOTTED    FEVER.  8 1 

a  considerable  amount  of  pale  bluish-staining  material  (Figs. 
24  and  25).  The  study  of  the  parasite  in  the  circulating  blood 
has  been  inadequately  done  by  myself.  In  one  human  case 
(Case  II.  of  this  report),  they  were  found  in  endothelial  cells 
in  ordinary  blood  films,  stained  with  Giemsa's  stain,  a  few 
hours  before  death  (Fig.  56).  I  have  studied  them  fre- 
quently in  thick  filmpreparations  from  monkeys  and  guinea- 
pigs,  but  have  been  unable  to  add  anything  to  the  above 
description.  I  have  never  been  able  to  find  them  during  the 
incubation  period,  but  have  found  them  to  be  rather  more 
abundant  towards  the  end  of  the  febrile  period  than  earlier 
in  the  disease,  and  it  is  my  belief  that  this  form  of  the  parasite 
exists  in  the  circulating  blood  only  within  phagocytic  cells, 
and  that  their  introduction  into  the  circulation  is  fortuitous, 
and  accounted  for  by  the  detachment  of  endothelial  cells 
from  the  lesions  in  the  blood  vessels. 

2.  The  parasite  in  the  tick  (Plates  VI.  to  IX).  —  In  ticks 
three  morphological  forms  can  be  found.  Inspection  of  the 
table  accompanying  the  study  of  the  parasite  in  ticks  infected 
as  nymphs,  shows  that  the  first  appearance  of  the  micro- 
organism occurs  on  and  after  the  fifth  day.  As  seen  in  smears 
of  the  gut  contents,  these  organisms  appear  as  pale-blue 
bacillary  forms  (Figs.  20  and  34),  some  of  which  are  slightly 
curved  and  club-shaped,  without  chromatoid  granules.  The 
distinctive  feature,  however,  is  the  delicacy  with  which  they 
stain,  and  their  pale-blue  coloration  with  Giemsa's  stain. 
In  size,  the  individual  rods  are  one  half  to  slightly  over  a 
micron  in  length.  These  forms  in  ticks  have  been  found  with 
constancy  only  in  the  gut  of  nymphs,  and  were  first  found 
in  a  day-to-day  examination  of  infected  nymphs,  undertaken 
in  the  hopes  of  demonstrating  a  life  cycle  for  the  parasite- 
In  the  tissues  of  ticks  infected  as  adults,  these  forms  have 
been  seen,  and  at  first  were  disregarded  because  it  seemed 
possible  that  they  were  not  connected  with  the  parasite  of 
spotted  fever.  An  adequate  series  of  controls  shows  that 
they  are  one  form  of  the  spotted  fever  parasite,  and  that 
their  presence  in   the  nymph   precedes  the  occurrence  of  a 


82  WOLBACH. 

smaller  delicately-staining  bluish  rod  with  deeply-staining 
chromatoid  granules.  This  minute  form  of  the  parasite 
(Figs.  21,  22,  28,  33,  35)  appears  in  smears  in  abundance  on 
and  after  the  seventh  day,  but  are  most  numerous  from  the 
seventh  to  the  fifteenth  day.  They  make  their  appearance 
earlier  in  nymphs  kept  at  37.5°  C.  than  at  room  temperature. 
These  forms  are  so  small  that  it  is  difficult  to  study  them 
except  with  high  magnification  and  perfect  illumination. 
The  1.5  millimeter  Zeiss  apochromatic  objective,  and  a 
6  compensating  ocular  represents  the  magnification  required. 
The  chromatoid  dots  in  these  minute  rods  are  often  paired 
and  are  usually  situated  at  one  end.  Appearances  are  found 
which  would  indicate  that  these  rods  divide  by  transverse 
fission,  and  that  the  division  is  preceded  by  a  division  of  the 
chromatoid  particles,  but  such  evidence  is  purely  morpho- 
logical. Later  on,  in  smear  preparations  of  the  gut  and  of 
other  organs  (Fig.  30),  the  more  deeply  staining  purplish 
lanceolate  paired  organisms  are  found.  In  adult  tissues  these 
exceedingly  minute  rods  with  chromatoid  dots  have  been 
found  only  in  smear  preparations  of  the  Malpighian  tubes 
and  salivary  glands.  In  sections  of  ticks,  whether  infected 
in  the  nymphal  or  adult  stage,  all  tissues  become  invaded 
by  the  parasite,  and  in  sections  of  ticks  one  can  distinguish 
at  least  two  morphological  types,  the  larger  lanceolate  form, 
which  becomes  universally  distributed  in  all  tissues,  and  a 
much  more  minute  form,  which  occurs  in  the  nuclei  of  cells 
and  occasionally  packed  in  the  muscle  fibers  of  the  intestinal 
tract  (Figs.  37  and  43).  The  larger  forms  have  been  found 
In  abundance  in  all  parts  of  the  intestinal  tract  and  the 
salivary  glands  (Figs.  36  and  38),  and  walls  of  the  salivary 
gland  ducts,  in  all  parts  of  the  reproductive  system,  male  and 
female,  and  have  been  found  both  in  spermatozoa  and  in  ova. 
The  brain  and  nerve  trunks  (Figs.  31  and  39)  and  musculature 
of  the  tick  (Fig.  40),  including  muscles  of  the  sucking  organs, 
leg  muscles  and  dorso-ventral  muscles,  become  heavily  in- 
fected. The  parasites  are  found  often  in  great  abundance 
in  the  cardiac  muscles  and  in  the  striated  muscle  of  the  aorta. 
In  the  salivary  glands  the  parasites  are  found  in  both  types 


ROCKY   MOUNTAIN    SPOTTED    FEVER.  83 

of  acini,  and  a  few  can  always  be  demonstrated  in  the  lumina 
of  the  intra-acinal  portions  of  the  ducts. 

The  intranuclear  (Figs.  2'],  32  and  42)  forms   are  exceed- 
ingly minute  and  are  often  found  completely  filling  and  even 
distending    the    nucleus.     Because    of    their    small    size    and 
tight  packing,  such  masses  even  in  thin  sections  are  difficult 
to   resolve   into   their   individual   members.     Occasionally   in 
such    intranuclear   masses   of    the   organisms,    a   few   larger 
lanceolate  paired  forms  will  be  found,  surrounded  by  a  very 
thin  clear  space  or  halo   (see  Fig.  27).     When  these  intra- 
nuclear  forms   were   first   encountered,    they   were   accepted 
with  reluctance  as  a  form  of  the  spotted  fever  parasite,  but 
I  now  regard  them  as  the  most  characteristic  form  in  infected 
ticks.     As  Tables  IV.  and  V.  show,  small  bacteria  are  fre- 
quently found  in  ticks,  but  in  no  uninfected  tick  has  this  mi- 
nute intranuclear  form  been  encountered.     The  distribution  of 
infected  nuclei  in  adult  ticks  is  restricted,  as  far  as  I  have 
been  able  to  determine,  to  the  Malpighian  tubes,  rectal  sac, 
intestinal  epithelium  and  the  cells  of  the  salivary  gland  ducts. 
In  nymphs  sectioned  during  the  quiescent  period,  they  have 
been  found  in  great  abundance  in  the  nuclei  of  the  hypoderm, 
which  at  this  stage  is  in  active  proliferation  in  the  formation 
of  new  organs.     They  have  been  also  found  in  the  musculature 
of   the  developing  adult,   as  well  as  in   the  other  locations 
mentioned.     The  infected  nuclei  are  found  with  greatest  ease 
and  earliest  in  the  epithelium  forming  the  valve-like  junction 
of  rectum  and  rectal  sac.     In  infected  ticks  that  have  been 
kept  for  several  months,  the  parasites  are  less  abundant  than 
during   the   first   few   weeks.     The   larger   lanceolate   forms,, 
however,   can   always  be  found  in   the  various  organs,   and 
usually  the  intranuclear  forms  can    be  found    in  the  rectal 
sac  and  Malpighian  tubes.     It  seems  probable  that  the  minute 
forms  found  in  such  numbers  in  the  smear  preparations  of 
engorged  nymphs  are  the  same  as   the    intranuclear    forms 
and  have  been  liberated  by  the  rupture  of  cells  in  the  making 
of  the  preparations.     In  support  of  this  point  is  the  fact  that 
in  one  instance  I  have  been  able  to  find  masses  of  minute 


84  WOLBACH. 

rods  with  chromatoid  granules,  lying  apparently  partly  en- 
closed by  the  nucleus  in  a  smear  preparation. 

There  is  no  cellular  reaction  to  the  parasite  of  Rocky 
Mountain  spotted  fever  in  the  tick.  An  absence  of  reaction 
to  relapsing  fever  spirochaetes  (Spirochceta  duttoni)  in  Ornitho- 
dorus  has  been  noted  by  me.^^ 

3.  The  parasite  in  the  eggs  of  ticks.  —  Ricketts  records 
experiments  in  which  the  disease  was  produced  by  the  in- 
jection of  eggs  from  infected  ticks,  an  experiment  which  I 
have  repeated  with  positive  results.  The  eggs  came  from 
Tick XXXII.,  infected  in  Montana  on  Case  II.,  and  afterwards 
used  to  establish  the  disease  in  Boston.  Companion  ticks 
are  XXXIII.  and  XXXIV.,  which  are  recorded  under  "  Adult 
ticks  proved  to  be  infective."  This  tick  became  fully  en- 
gorged while  feeding  on  Hayes  Guinea  Pig  3,  June  2  to  June 
II,  1917.  On  June  28,  1918,  one  hundred  and  forty  eggs  from 
this  tick  were  crushed  and  suspended  in  citrate  saline  solution, 
and  injected  subsequently  into  a  male  guinea-pig.  This 
guinea-pig,  after  an  incubation  period  of  seventy-two  hours, 
developed  and  ran  a  typical  course  of  Rocky  Mountain  spotted 
fever,  and  from  it  the  strain  was  re-inoculated  for  two  sub- 
sequent passages. 

The  larger  lanceolate  form  of  the  parasite  was  found  in 
smear  preparations  made  from  these  eggs  (Fig.  26).  This 
morphology  is  entirely  different  from  that  of  rods  in  the 
eggs  of  uninfected  ticks.  Figure  23  illustrates  the  forms  fre- 
quently encountered  in  eggs  from  non-infective  ticks,  and 
was  drawn  from  a  preparation  made  by  Prof.  R.  A.  Cooley 
and  identified  by  him  as  identical  with  those  described  by 
Ricketts.  This  non-pathogenic  bacterium  may  of  course 
occur  together  with  the  spotted  fever  parasite,  and  it  is  prob- 
able that  Ricketts  had  the  misfortune  to  work  extensively 
with  ticks  infected  with  this  organism. 

4.  Summary.  • — •  In  lesions  of  the  blood  vessels  in  man, 
monkeys,  rabbits  and  guinea-pigs,  the  larger  paired  lanceolate 
form  of  the  parasite  is  invariably  present.     On  Charts  i  to  5 


ROCKY   MOUNTAIN    SPOTTED    FEVER.  85 

inclusive,  the  guinea-pigs  which  have  been  examined  histo- 
logically for  the  parasites  are  indicated  by  a  check  (\/),  and 
without  exception  the  parasites  have  been  found.  As  the 
protocols  of  the  experiments  show,  they  were  found  in  all 
of  the  five  human  cases,  and  in  all  of  the  few  monkeys  and 
rabbits  examined.  The  guinea-pig  series  is  of  special  value. 
As  will  be  seen  by  the  chart,  the  parasite  was  found  in  all 
strains  of  the  virus  and  in  many  instances  after  one  or  more 
passages  of  the  virus  through  ticks;  in  the  case  of  the  Hayes 
strain  it  was  found  in  guinea-pigs  infected  after  three  passages 
of  the  virus  through  ticks. 

In  ticks  the  only  conclusion  possible  from  the  following 
experiments  is  that  this  organism  is  pathognomonic  of  and 
inseparable  from  ticks  capable  of  transmitting  Rocky  Moun- 
tain spotted  fever.  Some  significance  must  be  attached  to 
the  various  morphological  types  described,  and  the  sequence 
in  which  they  appear.  The  initial  form  in  infected  ticks  is 
the  relatively  large  delicately-staining  rod  without  chromatoid 
granules,  followed  by  an  exceedingly  minute  rod  form  with 
chromatoid  granules.  The  final  form  is  the  relatively  large, 
apparently  chromatin-rich  lanceolate  paired  form.  It  seems 
logical  to  believe  that  this  last  form  represents  a  resting  or 
perhaps  a  slightly  more  resistant  stage,  as  it  is  the  only  form 
that  can  be  demonstrated  in  the  circulating  blood.  The 
possibility,  however,  must  be  considered  of  another  form  in 
the  blood.  If  the  minute  rod  with  chromatoid  granules  or 
the  intranuclear  form  does  exist  in  the  circulating  blood,  free 
or  in  leucocytes,  its  demonstration  will  be  a  matter  of  diffi- 
culty. I  am  inclined  to  believe,  if  it  does  exist,  that  it  occurs 
within  leucocytes.  I  have  made  repeated  and  careful  attempts 
to  demonstrate  this  form  in  the  blood  without  success. 

The  study  of  blood  from  infected  animals  with  the  dark 
field  illuminating  apparatus  has  proved  futile.  All  of  the 
forms  described  in  ticks,  however,  can  be  seen  in  preparations 
from  tick  tissues.  They  are  difficult  to  see  in  the  gut  con- 
tents because  of  the  innumerable  large  refractive  granules 
which  are  products  of  digestion.  They  are  likewise  difficult 
to  see  in  preparations  from  .the  salivary  gland  because  of  the 


86  WOLBACH. 

granules,  probably  of  an  enzyme  nature,  with  which  the 
Type  I.  gland  cell  is  filled.  However,  they  have  been  found 
in  all  of  the  tissues  of  the  tick  by  this  method.  They  are 
not  motile.  One  characteristic  worthy  of  note  is  that  the 
contour  of  the  organism  with  the  dark  field  illumination  does 
not  present  the  refractive  contour  shown  by  bacteria.  The 
■organism  appears  as  an  evenly  illuminated  short  rod  exhibit- 
ing the  same  luminosity  and  contour  shown  by  spirochsetes ; 
for  this  comparison  Spirochceta  duttoni  was  used. 

5.  Nature  of  the  parasite.  —  A  decisive  conclusion  in  regard 
to  the  nature  of  this  parasite  is  not  justified  by  the  data  we 
have,  if  by  classification  we  mean  associating  it  with  other 
known  parasites,  as  bacterium,  protozoan  and  spirochaeta. 
The  simple  life  cycle  and  the  bacterium-like  morphology  are 
against  classifying  it  among  the  protozoa.  The  morpho- 
logical variations  which  I  have  described  do  not  represent  a 
greater  range  than  that  exhibited  by  many  well-known  bac- 
teria, but,  on  the  other  hand,  there  is  a  definite  morphological 
sequence  to  be  observed  in  infected  ticks  and  a  more  or  less 
specific  localization  in  the  tissues  of  ticks  of  the  various 
morphological  forms.  The  extreme  susceptibility  to  physical 
and  chemical  agents  may  be  accepted  as  a  weak  argument 
against  classification  with  bacteria.  The  staining  reaction 
which  has  been  dwelt  upon  in  the  description  is  another 
weak  argument,  but  one  nevertheless  upon  which  I  am  in- 
clined to  place  some  weight,  particularly  after  comparison 
with  many  bacteria  stained  by  similar  technic.  Even  with 
bacteria  as  small  as  the  influenza  bacillus  the  difference  in 
^staining  is  marked.  The  viable  bacteria  always  present 
sharply  defined  outlines  and  stain  much  more  intensely,  and 
when  treated  in  exactly  the  same  manner  employed  for  the 
spotted  fever  spiears,  invariably  stain  a  deep  purplish.  It  is 
true,  however,  that  some  bacteria  in  cultures  stain  bluish 
and  exhibit  chromatoid  granules,  but  not  with  the  same 
regularity  as  the  spotted  fever  organisms.  The  fact  that 
the  spotted  fever  parasite  is  always  intracellular  in  mammalian 
and  tick  tissues,  and  also  intranuclear  in  the  latter,  may  be 


ROCKY    MOUNTAIN    SPOTTED    FEVER.  87 

used  as  an  argument  against  its  bacterial  nature,  and  does, 
I  believe,  carry  some  weight,  but  bacteria  in  animal  tissues 
often  are  intracellular,  and  may  occur  there  in  large  numbers. 
Recently  Theobald  Smith^"*  and  Tyzzer^^  have  called  attention 
to  bacteria  characteristically  intracellular.  In  my  own 
studies  of  ticks,  bacteria,  whenever  encountered,  have  been 
intracellular,  frequently  in  large  numbers  (see  Tables  IV.  and 
v.),  though  never  intranuclear.  The  sum  of  the  weight  of 
these  differences,  together  with  the  very  unusual  feature 
exhibited  in  the  exact  reproduction  of  the  disease  in  experi- 
mental animals,  leads  me  to  the  conclusion  that  this  parasite 
represents  a  new  form  of  microorganism.  All  things  taken 
into  consideration,  including  the  fact  of  tick  transmission,  we 
have  but  a  single  reason  for  considering  the  classification  of  this 
organism  with  bacteria,  and  that  is  its  bacterium-like  mor- 
phology. It  would  be  egotistical  to  assume  that  I  have 
excluded  all  possibilities  in  the  way  of  a  more  complicated 
life  cycle.  All  that  I  have  accomplished  is  to  show  that  the 
various  stages  encountered  explain  the  facts  that  are  requisite 
to  account  for  the  multiplication  in  ticks  and  the  transmission 
of  the  disease.  It  seems  extremely  probable  that  certain 
spirochaetes,  such  as  the  relapsing  spirochaete,  have  a  definite 
life  cycle,  or  at  least  another  morphological  form,  yet  repro- 
duction by  transverse  division  is  sufficient  to  account  for  all 
of  the  phenomena  associated  with  the  transmission  of  the 
disease  by  ticks. ^^ 

Convinced  that  the  microorganism  of  Rocky  Mountain 
spotted  fever  represents  a  new  type  of  parasite,  I  propose 
the  name  Dermacentroxenus  (Dermacentor  -f  ^cVos)  rickettsi 
for  this  organism,  in  honor  of  Ricketts  who  first  saw  it  in  the 
blood.  The  name  "  Rickettsia  "  has  been  applied  by  da 
Rocha-Lima^^  to  minute  bacillary  forms  found  by  Hegler  and 
von  Prowazek  in  typhus  fever,  and  regarded  as  identical  with 
bodies  described  by  Ricketts^^  in  Mexican  typhus.  The 
available  descriptions  of  Ricketts  are  too  meager  to  permit  a 
trustworthy  comparison  with  the  spotted  fever  parasite,  but 
as  Ricketts's  description  of  the  typhus  organism,  which  he 
regarded   as   a   bacterium   of   the   plague   bacillus   group,    is 


88  WOLBACH. 

markedly  different  from  his  description  of  the  spotted  fever 
organism  in  blood,  the  name  "  Rickettsia  "  cannot  be  con- 
sidered as  applicable  to  the  spotted  fever  organism,  as  de- 
scribed in  this  report.  Much  more  work  is  required  before 
the  classification  of  "  Rickettsia  "  and  its  relation  to  typhus 
fever  can  be  arrived  at. 

6.  Attempts  at  cultivation. — After  the  demonstration  of 
the  minute  organisms  in  the  lesions  of  the  blood  vessels  in 
guinea-pigs  and  monkeys,  a  series  of  cultivation  experiments 
was  begun,  which  was  carried  through  two  years  until  every 
possible  method  was  tried.  Ricketts  apparently  made  ex- 
haustive attempts  at  cultivation  of  the  virus  without  success. 
Fricks^^  claims  to  have  infected  guinea-pigs  with  cultures 
grown  under  partial  anaerobic  conditions  in  human  blood 
serum  diluted  with  normal  salt  solution  in  the  proportion  of 
one  to  two  and  three.  A  piece  of  fresh  guinea-pig  kidney  was 
added  to  the  medium  at  the  time  of  inoculation.  In  the 
three  guinea-pigs  which  acquired  the  disease,  the  cultures 
were  inoculated  with  blood  from  a  guinea-pig,  blood  from  a 
human  case,  and  crushed  tick  eggs  respectively.  I  have  been 
unable  to  repeat  these  results,  and  indeed  have  found  it 
impossible  to  make  the  virus  survive  in  any  culture  medium 
for  a  period  equal  to  that  in  defibrinated  blood. 

All  of  the  ordinary  bacteriological  media  have  been  tried 
under  all  conditions  of  temperature  and  oxygen  supply.  The 
various  methods  for  securing  partial  anaerobiasis  successful 
in  the  cultivation  of  Bacillus  abortus  were  employed  without 
success.  The  methods  of  growing  spirochaetes  devised  by 
Noguchi  were  tried,  and  in  these  experiments  the  criterion 
for  a  suitable  ascitic  fluid  was  the  successful  cultivation  of 
SpirochcBta  duttoni.  Several  liquid  and  solid  media  con- 
taining hemoglobin  which  proved  to  be  suitable  for  the  culti- 
vation of  Trypanosoma  lewisi  were  used,  including  the  Novy- 
McNeil-Nicolle  medium,  and  the  medium  used  by  myself. 
Chapman  and  Stevens^^  for  growing  trypanosomes  for  filtra- 
tion experiments.  A  variety  of  bacteria  and  mold  fungi  were 
used  in  the  hope  of  finding  a  method  of  cultivation  in  symbio- 
sis.    A  few  experiments  were  even  made  with  tissue  cultures 


ROCKY   MOUNTAIN    SPOTTED    FEVER.  89 

which  was  done  with  the  assistance  of  Dr.  N.  C.  Foot.  Suc- 
cessful tissue  cultures  were  started  from  tissues  excised  from 
the  testicle  and  epididymis  of  infected  guinea-pigs.  No  or- 
ganisms could  be  demonstrated  in  the  tissue  cultures,  which 
were  composed  chiefly  of  connective  tissue  cells;  nor  was  it 
possible  to  infect  animals  by  injecting  the  whole  of  these 
cultures.  Two  series  of  cultivation  experiments  were  carried 
through,  using  relatively  simple  media  containing  unheated 
protein,  in  which  especial  attention  was  paid  to  securing  a 
wide  range  of  reaction,  in  the  hope  that  success  might  be 
achieved  at  a  certain  hydrogen-iron  concentration. 

In  all  of  the  above  experiments  the  dark  field  illuminating 
apparatus  was  used  in  studying  the  cultures.  From  time  to 
time  guinea-pig  inoculations  were  made,  even  though  the 
morphological  evidence  was  negative.  Occasionally  bacteria 
were  encountered,  which  when  injected,  caused  a  fatal  peri- 
tonitis or  a  septicaemia.  The  most  striking  instance  of  this 
sort  was  the  recovery  of  a  small  streptococcus  which  was  fatal 
for  guinea-pigs  in  about  six  days  after  inoculation.  This 
streptococcus  grew  best  under  anaerobic  conditions,  and  caused 
a  course  of  temperature  somewhat  similar  to  that  produced 
by  spotted  fever. 

As  success  in  the  cultivation  of  pathogenic  microorganisms 
may  depend  on  very  slight  variations  in  the  constitution  of 
culture  media  —  acidity  and  oxygen  supply  —  the  publication 
of  negative  results  does  not  seem  advisable,  as  it  might  tend 
to  discourage  repetition,  whereas  repeated  efforts  may  result 
in  the  accidental  or  intentional  introduction  of  the  necessary 
factors.  On  the  other  hand,  the  problem  may  be  as  impossible 
of  solution  as  the  cultivation  of  the  bacillus  of  leprosy  has 
proved  to  be. 

XIII.        EXPERIMENTS     TO     PROVE     THE     SPECIFICITY     OF      THE 

PARASITE. 

Since  the  proof  of  the  causal  relationship  of  the  microor- 
ganism which  I  have  described  is  largely  dependent  upon 
its  constant  occurrence  and  inseparability  from  ticks  capable 


■90  WOLBACH. 

of  transmitting  the  disease,  the  results  have  been  tabulated 
together  with  the  control  experiments  under  the  following 
headings: 

(i)  Adult  ticks  proved  to  be  infective. 

(2)  Ticks  infected  as  nymphs,  some  of  which  were  proved 
to  be  infective  in  the  adult  stage. 

(3)  Control  ticks,  nymphs,  first  series  and  second  series. 

(4)  Adult  control  ticks  proved  non-infective. 

(5)  Adult  control  ticks  not  tested. 

In  every  instance  of  adult  ticks  proved  to  be  infective,  the 
parasites  were  found.  They  were  found  in  no  instance  in 
proved  non-infective  ticks,  either  in  adults  or  nymphs.  In 
infected  nymphs  they  were  found  in  every  instance  where 
the  examinations  were  made  later  than  six  days  after  dropping, 
with  one  exception  —  Tick  LXXXIV.  — which  was  not  thor- 
oughly examined. 

In  the  examination  of  adult  control  ticks  which  were  not 
tested,  some  of  which  were  obtained  by  dragging  in  the  unfed 
state,  and  others  in  various  degrees  of  engorgement  collected 
from  cattle,  bacteria  were  found  in  a  fair  number.  Unfed 
adult  ticks  in  the  spring  months  will  collect  upon  cloth  dragged 
over  vegetation,  as  moving  objects  represent  possible  hosts. 
In  only  one  instance  were  microorganisms  found  which  could 
he  confused  with  the  spotted  fever  parasite.  This  was  in 
Tick  XI.,  Table  V.,  which  came  from  an  unengorged  male, 
one  of  a  series  collected  from  cattle.  It  is  possible  that  this 
was  a  naturally  infected  tick.  On  the  other  hand,  the  distri- 
bution of  the  organisms  was  limited  to  the  epithelial  cells  of 
the  intestinal  tract,  while  I  have  Invariably  found  the  organ- 
isms much  more  widely  distributed  in  proved  infected  ticks. 

In  addition  to  the  ticks  recorded  In  table  form,  twenty 
adult  ticks  fed  once  upon  infected  guinea-pigs,  but  not  tested 
after  their  infectivlty,  were  examined  for  the  parasites.  They 
were  found  in  eleven  of  these  twenty  ticks,  which  in  view  of 
the  fact  of  the  frequent  failure  to  Infect  ticks  by  one  or  even 
two  feedings,  is  about  what  one  would  expect.  In  one  tick, 
which  failed  to  produce  the  disease  after  each  of  two  feedings 
and  which  was  fed  a  third  time  on  an  infected  guinea-pig. 


ROCKY    MOUNTAIN    SPOTTED    FEVER.  9I 

the  parasites  were  found.  The  infectivity  of  this  tick  could 
not  be  tested,  as  it  became  fully  engorged  during  the  last 
feeding. 

The  conclusion  to  be  drawn  from  these  examinations  of 
infected  and  control  ticks  is  that  the  microorganism  under 
consideration  is  constantly  present  in  and  inseparable  from 
ticks  containing  the  virus  of  Rocky  Mountain  spotted  fever, 

(i)  Adult  ticks  proved  to  be  infective.  —  Tick  X.,  D.  venus- 
tus,  unfed.  Fed  June  20  to  June  22,  1916,  on  Strain  II. 
Guinea  Pig  34,  again  on  June  27  to  29,  1916,  on  Strain  II. 
Guinea  Pig  35.     (See  Chart  2.) 

Record  of  Strain  II.  Guinea  Pig  34,  inoculated  June  15,  1916,  from 
No.  31  of  this  series: 

Temperatures:  June  13,  102;  June  14,  103;  June  15,  102.5;  June  16, 
17,  18,  19,  104.6;  June  20,  106,  ticks  attached;  June  21,  104;  June  22, 
95,  ticks  removed. 

Killed  June  22,  1916.     Autopsy  showed  typical  lesions  of  spotted  fever. 

Record  of  Strain  II.  Guinea  Pig  35,  inoculated  June  21,  1916,  from 
No.  33  of  this  series: 

iT!^  Temperatures:  June  21,  22,  103.6;  June  23,  103;  June  24,  25,  26, 
105.6;  June  27,  106,  ticks  attached;  June  28,  105.6;  June  29,  dead,  ticks 
removed. 

An  autopsy  showed  typical  lesions  of  spotted  fever. 

This  tick  was  fed  July  15  to  18,  1916,  on  a  normal  guinea-pig  labeled 
Tick  X.  guinea-pig,  to  test  its  infectivity. 

Record  of  Tick  X.  Guinea  Pig.  —  Temperatures  after  removal  of 
Tick  X.:  July  18,  101.2;  July  19,  101.8;  July  20,  102.6;  July  21,  105; 
July  22,  105.8;    July  23,  24,  105.8,  killed. 

At  autopsy  the  lesions  were  typical  of  spotted  fever,  and  from  this 
guinea-pig  the  strain  was  maintained  for  sixteen  generations.  (See  Chart 
2.) 

Result:  Tick  X.  proved  to  have  transmitted  the  virus  of 
Rocky  Mountain  spotted  fever. 

July  24,  1916,  dissected  and  tissues  preserved  for  serial 
section.  The  organisms  were  found  in  the  sections  in  the 
salivary  glands  and  duct  walls,  gut  walls,  Malpighian  tubes, 
ganglion  and  nerves  and  musculature. 

Tick  XL,  D.  venustus,  unfed.  Fed  June  20  to  22,  1916, 
and  again  on  June  27  to  29,  1916,  on  Strain  II.  Guinea  Pigs  34 
and  35,  together  with  Tick  X.     (See  Chart  2.) 


92  WOLBACH. 

This  tick  was  fed  July  i5to  i8,  1916,  on  a  normal  guinea-pig,  labeled 
Tick  XI.  Guinea  Pig,  to  test  its  infectivity.  The  result  was  negative  as 
shown  by  the  temperatures  after  removal  of  the  tick. 

Temperatures:  July  18,  101.5;  July  19,  102;  July  20,  101.8;  July  22,. 
102;  July  24,  101.8;  July25,  loi;  July  26,  101.9;  July  27,  101.6;  July  28, 
101.6;    July  29,  102. 

This  Tick  XL  Guinea  Pig  proved  susceptible  to  inoculation  from  Tick 
X.  Guinea  Pig  3,  from  which  it  was  inoculated  July  29,  and  it  was  re- 
corded as  Tick  X.  Guinea  Pig  5. 

Temperatures:  July  29,  102;  July  20,  102;  July  31,  104.8;  August  i, 
105;  August  2,  104.2;  August  3,  106;  August  4,  106.2;  August  5,  104.8, 
killed. 

The  autopsy  showed  typical  lesions  of  spotted  fever,  and  from  this- 
pig  Tick  X.  Guinea  Pigs  7  and  8  were  inoculated  in  perpetuating  the 
strain.      (See  Chart  2.) 

Third  feeding  of  Tick  XI.  on  an  infected  guinea-pig.  July  28,  1916, 
to  July  30,  1916,  this  tick  was  fed  with  three  other  ticks  upon  Tick  X. 
Guinea  Pig  2.     (See  Chart  2.) 

Record  of  Tick  X.  Guinea  Pig  2,  inoculated  July  24,  1916,  from  original 
Tick  X.  Guinea  Pig. 

Temperatures:  July  24,  102.2;  July  25,  100.6;  July  26,  102.4;  July 
27,  104.6;  July  28,  105,  ticks  attached;  July  29,  30,  31,  dead,  ticks  removed.. 

At  autopsy  the  lesions  were  typical  of  spotted  fever. 

Second  feeding  on  a  normal  guinea-pig,  August  2  to  7,  19 16.  This 
Tick  XI.  was  fed  August  2  to  7,  1916,  for  the  second  time  on  a  normal 
guinea-pig,  recorded  as  Tick  XI.  guinea-pig  of  August  2. 

Record  of  Tick  XI.  guinea-pig  of  August  2,  after  removal  of  Tick  XL 

Temperatures:  August  7,  106;  August  8,  106.4;  August  9,  106; 
August  10,  106;  August  II,  105.8,  scrotum  swollen  and  red,  eyelids  and 
paws  are  swollen,  the  scrotum  is  swollen  and  black;  August  12,  103.6; 
August  13,  dead. 

At  autopsy  the  lesions  were  typical  of  spotted  fever. 

Result:  Tick  XI.  proved  to  have  transmitted  the  virus  of 
Rocky  Mountain  spotted  fever. 

Tick  XI.  dissected  August  12,  1916.  Smear  and  dark  field, 
preparations  were  made  from  one  side  and  the  remainder- 
preserved  for  serial  sections. 

The  organisms  were  found  by  all  methods  in  salivary  glands,, 
musculature  and  Malpighian  tubes.  In  serial  sections  they 
were  found  in  all  organs  and  also  in  spermatozoa.  (Figs.  28, 
37  and  43.) 

Tick  XIII.,  D.  venustus,  unfed  9  .  Fed  July  13  to  15,  1916, 
on  Strain  I.  Guinea  Pig  162. 

Record  of  Guinea  Pig  162;  inoculated  July  7  from  No.  159:. 


ROCKY   MOUNTAIN    SPOTTED    FEVER.  93 

Temperatures:  July  8,  103;  Jul)'  li,  104.2;  July  12,  104.5,  ticks 
attached;   July  14,  loi;   July  15,  dead,  discarded. 

This  Tick  XIII.  was  fed  on  a  normal  guinea-pig,  recorded  as  Tick  XI II 
Guinea  Pig,  July  18  to  20,  1916.     Result  negative. 

Record  of  guinea-pig  after  removal  of  tick:  July  20,  101.3;  July  21, 
99;  July  22,  lOi;  July  24,  101.2;  July  25,  101.8;  July  26,  101.2;  July 
27  101.4;  July  28,  100.6;  July  29,  loi;  July  30,  102;  July  31,  102.4; 
August  I,  102.4;   August  2,  101.6. 

This  guinea-pig  was  inoculated  August  2  from  Strain  I.  Guinea  Pig 
176  and  was  recorded  as  No.  179,  and  proved  susceptible.  It  was  used  to 
infect  other  ticks.  At  death,  August  11,  1916,  presented  typical  lesions 
of  spotted  fever. 

Second  feeding  of  Tick  XIII.  on  an  infected  guinea-pig.  July  28  to 
July  30,  1916,  fed  on  Tick  X.  Guinea  Pig  2,  together  with  Tick  XI.  (See 
above.) 

Second  feeding  of  Tick  XIII.  on  a  normal  guinea-pig.  Fed  August  2 
to  7,  1916,  on  a  normal  guinea-pig,  during  which  time  it  became  fully 
engorged 

Record  of  Tick  XIII.  Guinea  Pig  of  August  2:  Temperatures  after 
removal  of  tick:  August  7,  104.4;  August  8,  105.2;  August  9,  106.4; 
August  10,  105.8;  August  II,  105.6;  August  12,  105.8;  August  13,  14, 
105;  August  15,  104;  August  16,  104;  August  17,  103;  August  18,  102.6, 
killed. 

At  autopsy  the  lesions  were  typical  of  spotted  fever,  with  necrosis  of 
paws  and  swelling  of  eyelids  and  paws.  The  tissues  studied  microscopi- 
cally showed  the  histological  lesions  and  the  microorganisms  in  the  blood 
vessels  which  are  characteristic  of  spotted  fever. 

Result:  Tick  XIII.  proved  to  have  transmitted  the  virus 
of  Rocky  Mountain  spotted  fever. 

Dark  field  preparations  showed  the  organisms  in  the  leg 
muscles.  Serial  sections  showed  the  organisms  in  all  tissues. 
In  smears  they  were  found  in  salivary  gland,  muscle  and 
Malpighian  tubes.     (Figs.  33  and  36.) 

Tick  XIV.,  D.  venustus,  unfed  9  •  Fed  July  12  to  15,  1916, 
on  Strain  II.  Guinea  Pig  39. 

Record  of  Strain  II.  Guinea  Pig  39.  Inoculated  July  7 
from  Guinea  Pig  37  of  this  series.     (See  Chart  2.) 

Temperatures:  July  8,  103;  July  11,  104;  July  12,  104.2,  ticks 
attached;  July  13,  104.3;  July  14,  105.6,  scrotum  swollen  and  red;  July 
15,  106,  killed  for  inoculations,  ticks  removed. 

Guinea  Pigs  40  and  41  inoculated  from  this  guinea-pig  ran  typical 
courses  of  the  disease  (see  Chart  2.),  and  from  them  the  strain  was  con- 
tinued. 

This  Tick  XIV.  was  fed  on  a  normal  guinea-pig  recorded  as  Tick  XIV. 
Guinea  Pig,  July  18  to  20,  1916,  with  negative  result. 


94  WOLBACH. 

Record  of  Tick  XIV.  Guinea  Pig.  Temperatures  after  removal  of 
tick:  July  20,  102.3;  July  21,  102.4;  July  22,  102.6;  July  23,  24,  102; 
July  25,  102.2;  July  26,  101.2;  July  27,  102.2;  July  28,  101.8;  July  29, 
102.2;    July  30,  102.4;    July  31,  102.6;    August  i,  102.8;    August  2,  102.8. 

This  guinea-pig  was  inoculated  August  2,  1916,  from  Strain  I.  Guinea 
Pig  176,  and  recorded  as  No.  180.     It  proved  susceptible. 

Record  of  Guinea  Pig  180.  Temperatures:  August  2,  102.8;  August  3, 
103.2;  August  4,  102.6;  August  5,  103.6;  August  7,  105;  August  8, 
105.6,  scrotum  swollen. 

Killed  August  8.     Autopsy   showed   typical  lesions  of  spotted   fever, 
and  Guinea  Pigs  181,  182  and  183  inoculated  from  it  developed  the  disease.  . 
(See  Chart  i.) 

Second  feeding  of  Tick  XIV.  on  an  infected  guinea-pig.  July  28  to 
30,  1916,  fed  on  Tick  X.  Guinea  Pig  2,  together  with  Ticks  XI.  and  XIII. 
(See  above.) 

Second  feeding  of  Tick  XIV.  on  a  normal  guinea-pig.  Fed  August  2 
to  August  7,  1916,  on  a  normal  guinea-pig,  on  which  it  became,  fully  en- 
gorged. 

Record  of  Tick  XIV.  Guinea  Pig  of  August  2.  Temperatures  after 
removal  of  tick:  August  7,  102.2;  August  8,  103;  August  9,  104;  August 
ID,  106;  August  II,  106.1;  August  12,  105.8,  scrotum  swollen  and  red. 
August  13,  14,  105.2;  August  15,  105.2;  August  16,  103.8;  August  17,, 
102.8;  August  18,  103,  scrotum  normal;  induration  at  site  of  bite;  August 
19,  102.8;  August  24,  102.8;  August  25,  102.8;  August  26,  103;  August 
27,  102;   August  30,  102;    September  i,  102. 

This  guinea-pig  was  inoculated  February  17,  1917,  from  Tick  XXVII. 
Guinea  Pig,  Darby  strain,  and  proved  to  be  immune. 

Result:  Tick  XIV.  proved  to  have  transmitted  the  virus 
of  Rocky  Mountain  spotted  fever. 

Tick  XIV.  dissected  August  22,  1916. 

The  organisms  were  found  in  smears  in  preparations  of  the 
gut,  sahvary  gland,  Malpighian  tubes  and  leg  muscles.  In 
serial  sections  they  were  found  in  all  tissues.  (Figs.  38,  40,. 
41  and  42.) 

Tick  XIX.,  D.  venustus,  unfed  cT.  Fed  on  Strain  I.  Guinea 
Pig  154,  June  26  to  29,  1916.     Inoculated  June  21  from  No.  150- 

Temperatures  of  Guinea  Pig  154:  June  22,  103;  June  23,  103. i;  June 
26,  107,  scrotum  swollen  and  red,  ticks  attached;  June  28,  106;  June 
29,  killed,  ticks  removed. 

Blood  from  this  guinea-pig  was  used  to  inoculate  No.  158  which  ran  a 
typical  course  and  was  used  to  continue  the  strain.  July  20  to  24,  1916, 
this  Tick  XIX.  was  fed  on  a  normal  guinea-pig  which  was  recorded  as 
Tick  XIX.  Guinea-Pig.  The  tick  fed  well  and  passed  considerable  feces. 
during  the  four  days. 


ROCKY    MOUNTAIN    SPOTTED    FEVER.  95 

Record  of  Tick  XIX.  guinea-pig  after  removal  of  the  tick:  July  24, 
101.8;  July  25,  103.4;  July  26,  102.7;  July  27,  103.8;  July  28,  105.8; 
July  29,  105.4,  scrotum  swollen  and  red;  July  30,  105.2;  July  31,  105.2?. 
August  I,  104.4;  August  2,  103.8;  August  3,  103,  scrotum  necrotic,  ears 
swollen  and  red,  paws  swollen  and  red;  August  4,  102.6;  August  5,  102; 
August  6,  102;  August  8,  102,  edges  of  ears  are  dry,  necrotic;  August 
9,  102;  August  10,  102;  August  II,  102.5;  August  12,  102.4;  August  13, 
14,  102.4. 

Result:  Tick  XIX.  proved  to  have  transmitted  the  virus 
of  Rocky  Mountain  spotted  fever.  Tick  XIX.  dissected 
July  28,  191 6.     Examined  by  serial  sections. 

The  organisms  were  found  in  all  tissues  in  small  numbers^ 
abundantly  in  the  salivary  glands,  oesophagus,  ganglion  and 
gut. 

Tick  XXL,  D.  venustus,  unfed  cT".  Fed  June  28  to  July  i,. 
1916,  on  Strain  I.  Guinea  Pig  156. 

Temperatures:  June  22,  10T.8;  June  26,  103. i;  June  28,  105.4,  ticks 
attached. 

This  tick  was  well  filled  as  the  result  of  this  feeding. 

July  20  to  24,  1916,  this  Tick  XXI.  was  fed  on  a  normal  guinea-pig 
which  was  recorded  as  Tick  XXI.  Guinea  Pig.  The  tick  became  well' 
filled  and  passed  much  feces. 

Record  of  Tick  XXI.  Guinea  Pig  after  removal  of  tick:  July  24,  102.4-, 
July  25,  104.6;  July  26,  106.2;  July  27,  105;  July  28,  106.4;  Ju'-Y  29, 
105.8;    July  30,  104.8.     July  31  was  found  dead. 

The  autopsy  showed  typical  lesions  of  spotted  fever. 

Result:  Tick  XXI.  proved  to  have  transmitted  the  virus 
of  Rocky  Mountain  spotted  fever.  Tick  XXI.  dissected 
July  28. 

The  organisms  were  found  in  serial  sections  in  salivary 
glands,  muscles  of  sucking  organ  and  brain  and  nerve  trunks. 
(Figs.  31  and  39.) 

Tick  XXVI.,  D.  venustus,  9 .  From  L.  D.  Fricks.  Fed  in 
nymphal  stage  in  summer  of  191 5  on  a  guinea-pig  inoculated 
from  a  human  case  of  Rocky  Mountain  spotted  fever.  "  Dar- 
by "  strain  series.  (See  Chart  3.)  Attached  to  a  normal 
guinea-pig,  recorded  as  Tick  XXVI.  Guinea  Pig,  December  27, 
1916,  to  January  3,  1917. 

Record  of  guinea-pig,  Tick  XXVI.  December  27,  tick  attached  in 
capsule;   December  28,  tick  not  feeding;    December  29,  tick  has  attached; 


96  WOLBACH. 

December  30,  31,  tick  has  passed  feces.  Temperatures:  January  r,  104; 
January  2,  104.2;  January  3,  105,  tick  removed;  January  4,  106,  killed 
for  inoculation. 

Autopsy  showed  typical  lesions  of  spotted  fever.  Two  other  guinea- 
pigs,  Nos.  2  and  3,  were  inoculated  with  blood  from  this  one,  and  ran 
typical  courses  and  at  autopsy  showed  lesions  typical  of  spotted  fever. 

Record  of  Tick  XXVI.  Guinea  Pig  2,  inoculated  January  4,  1917. 
Temperatures:  January  5,  102.2;  January  6,  101.6;  January  8,  105; 
January  9,  105;    January  10,  104;   January  11,  loi,  killed. 

Autopsy  showed  typical  lesions  of  spotted  fever. 

Record  of  Tick  XXVI.  Guinea  Pig  3,  inoculated  January  4,  1917. 
Temperatures:  January  5,  102;  January  6,  102;  January  8,  105;  January 
9,  105;   January  10,  104;   January  11,  103.4,  killed. 

Autopsy  showed  typical  lesions  of  spotted  fever. 

Result:  Tick  XXVI.  proved  to  have  transmitted  the  virus 
of  Rocky  Mountain  spotted  fever.  Tick  XXVI.  dissected 
January  12,  1917. 

Organisms  were  found  in  the  smear  preparations  of  the 
saHvary  gland,  Malpighian  tubes,  gut  and  leg  muscles.  In 
serial  sections  they  were  found  in  the  brain  and  salivary 
gland.     (These  sections  were  poorly  stained.) 

Tick  XXVIII.,  D.  venustus,  9  .  Same  source  as  Tick  XXVI. 
Attached  to  a  normal  guinea-pig,  recorded  as  Tick  XXVIII. 
Guinea  Pig,  December  27,  1916,  to  January  3,  1917. 

Record  of  Tick  XXVIII.  Guinea  Pig.  December  27,  tick  attached  in 
capsule;  December  28,  tick  not  feeding;  December  29,  tick  not -feeding; 
December  30,  31,  tick  feeding,  has  passed  feces;  January  i,  temperature 
of  guinea-pig,  100.8;  January  2,  temperature  of  guinea-pig,  102;  January 
3,  temperature  of  guinea-pig,  103.4,  tick  removed;  January  4,  tempera- 
ture of  guinea-pig,  104.4;  January  5,  temperature  of  guinea-pig,  106; 
January  6,  temperature  of  guinea-pig,  105.6,  killed. 

Autopsy  showed  typical  lesions  of  spotted  fever,  and  inoculation  of 
the  heart's  blood  reproduced  the  disease  in  two  other  guinea-pigs  from 
which  a  third  series  of  guinea-pigs  were  infected;  each  animal  reacted 
characteristically  and  showed  typical  lesions. 

Result:  Tick  XXVIII.  proved  to  have  transmitted  the 
virus  of  Rocky  Mountain  spotted  fever.  Tick  XXVIII.  dis- 
sected January  23,  191 7. 

The  organisms  were  found  in  smear  preparations  of  salivary 
glands,  Malpighian  tubes,  gut  wall  and  muscles. 

Tick  XXXIII.  and  Tick  XXXIV.  Two  unfed  D.  venus- 
tus 9  s.     Fed  with  others  May  22  to  May  24,  1917,  on  one 


ROCKY   MOUNTAIN    SPOTTED    FEVER.  97 

of  two  guinea-pigs  inoculated  with  one  cubic  centimeter  of 
blood  May  18,  1917,  from  a  human  case  of  spotted  fever  at 
Hamilton,  Mont.     (Case  III.,  John  Lake.) 

Temperatures  of  Case  III.  guinea-pig:  May  18,  inoculated;  May  19 • 
103.2;  May  21,  lOi;  May  22,  105,  ticks  attached;  May  23,  104.9; 
May  24,  105,  scrotum  swollen  and  red,  ticks  removed;    May  25,  killed. 

This  guinea-pig  was  not  autopsied.  The  companion  inoculated  at  the 
same  time  ran  a  similar  course  of  temperatures  and  at  autopsy,  May  25, 
showed  typical  lesions  of  spotted  fever. 

These  two  ticks  were  attached  in  a  capsule  on  June  2,  1917,  to  a  normal 
guinea-pig,  recorded  as  Case  III.  Guinea  Pig  3.     Removed  June  11,  1917. 

Record  of  Case  III.  Guinea  Pig  3.  —  Temperatures:  June  2,  ticks 
attached;  June  4,  102,  one  tick  feeding;  June  5,  103,  both  ticks  feeding; 
June  6,  102.2;  June  8,  101.8;  June  9,  101.2;  June  11,  101.6,  ticks 
removed;  June  12,  102.4;  June  13,  101.6;  June  14,  102;  June  15,  103.4; 
June  16,  104;  June  18,  104.6;  June  19,  105;  June  20,  105;  June  21, 
103;   June  22,  dead. 

Autopsy  showed  typical  lesions  of  spotted  fever. 

Result :  One  or  both  of  Ticks  XXXIII.  and  XXXIV.  proved 
to  have  transmitted  the  virus  of  Rocky  Mountain  spotted 
fever. 

Ticks  XXXIII.  and  XXXIV.  dissected  June  29,  1917. 

Both  ticks  showed  the  organisms  in  marked  abundance  in 
all  tissues  in  serial  sections  and  in  the  smear  preparations  of 
salivary  glands,  gut,  Malpighian  tubes  and  muscles.     (Fig.  30.) 

Summary:  Ten  proved  infective  adult  ticks  contained  the 
parasites  of  Rocky  Mountain  spotted  fever. 

(2)  Ticks  infected  as  nymphs,  some  of  which  were  proved 
to  be  infective  in  the  adult  stage.- — The  "  flat,"  i.e.,  unfed, 
nymphs  used  in  this  series  of  examinations  for  the  presence 
of  the  spotted  fever  organisms  were  received  from  W.  V.  King 
in  June,  1917.  These  nymphs  were  raised  by  Dr.  King  from 
eggs  and  reached  the  nymphal  stage  in  July,  1916.  Seven 
which  fed  on  a  normal  guinea-pig  (see  first  control  series, 
Table  II.)  did  not  infect.  On  July  2,  1917,  200  were  placed 
in  a  jar  with  Guinea  Pig  19,  Hayes  strain.  On  July  3,  127 
more  nymphs  were  added,  making  a  total  of  327.  On  July  5  , 
the  guinea-pig  with  the  feeding  nymphs  was  transferred  to  a 


98  WOLBACH. 

new  jar  and  the  first  one  sterilized.  On  July  9  many  fully 
engorged  nymphs  had  dropped,  and  on  July  11,  140  fully 
engorged  nymphs  were  collected  from  the  jar.  The  majority 
of  these  nymphs  molted  during  the  first  week  in  August,  and 
the  adults  reserved  for  future  experiments  were  placed  in  a 
cold  room,  in  a  slightly  moistened  atmosphere,  temperature 
7°  C.  to  10°  C. 

The  temperatures  of  this  guinea-pig  were  not  taken  because 
of  the  danger  of  losing  some  of  the  nymphs.  It  was  killed 
July  II,  191 7,  and  showed  the  typical  lesions  of  spotted  fever. 
The  inguinal  lymph  nodes  were  enlarged  and  red.  The  spleen 
was  treble  normal  size,  deep  red  in  color;  the  capsule  was 
covered  with  a  thin,  translucent  fibrinous  layer.  The  testes 
were  adherent  to  the  tunica,  with  hemorrhages  into  the  polar 
fat.  The  cremasteric  muscles  were  dry,  dark-red  in  color 
and  adherent.  The  skin  of  the  scrotum  was  necrotic  and  the 
subcutaneous  tissues  of  the  scrotum  were  oedema  tous  and 
dark-red  in  color.  The  other  tissues  of  the  guinea-pig  were 
negative. 

Experiments  to  prove  the  infectivity  of  the  ticks  fed  as 
nymphs  on  Hayes  Strain  Guinea  Pig  19.  —  I.  August  i"! , 
191 7,  placed  three  female  and  three  male  ticks  of  this  series 
in  a  wire  gauze  capsule  upon  a  normal  guinea-pig  subse- 
quently recorded  as  Hayes  Strain  Guinea  Pig  44.  (See  Chart 
4-) 

Record  of  Hayes  Strain  Guinea  Pig  44.  August  27,  ticks  attached;: 
August  28,  loi,  none  feeding;  August  29,  100,  all  ticks  feeding.. 
Temperatures:  August  30,  100;  August  31,  101.6;  September  i,  102.7;, 
September  3,  105.6;  September  4,  106,  removed  ticks;  all  have  fed  mod- 
erately;   September  5,  105.4,  killed  guinea-pig  for  inoculations. 

Autopsy  showed  the  typical  lesions  of  spotted  fever,  and  from  this 
guinea-pig  the  strain  was  maintained.      (See  Chart  4,  page  59.) 

Result:  Six  ticks  fed  as  nymphs  on  Hayes  Strain  Guinea 
Pig  19  proved  to  have  transmitted  the  virus  of  Rocky  Moun- 
tain spotted  fever. 

n.  August  23,  1 91 8.  Placed  two  female  »and  two  male 
ticks  of  this  series  in  a  wire  gauze  capsule  upon  a  normal; 


ROCKY   MOUNTAIN    SPOTTED    FEVER.  99 

guinea-pig,  subsequently  recorded  as  Hayes  Tick  Guinea  Pig 
of  August,  1918. 

Record  of  Hayes  Tick  Guinea  Pig  of  August,  1918.  Temperatures: 
August  23,  102.4,  ticks  attached;  August  24,  101.6,  three  ticks  feeding; 
August  25,  loi.i,  two  ticks  are  feeding;  August  26,  101.6,  all  ticks  are 
feeding;  some  have  passed  feces;  August  27,  100;  August  28,  104;  August 
29,  102.6,  removed  ticks;  all  have  fed  moderately;  August  30,  105.3, 
inoculated  Guinea  Pigs  i  and  2  with  blood  taken  by  heart  puncture; 
August  31,  106.6,  killed. 

The  autopsy  showed  the  typical  lesions  of  spotted  fever,  and  Guinea 
Pigs  3  and  4  inoculated  with  the  heart's  blood  were  used  to  maintain  the 
strain.  (See  Chart  5,  page  60.)  On  Guinea  Pig  13  of  this  series  other 
ticks  reared  from  eggs  of  a  tick  (Tick  A)  were  infected  and  Hayes  Tick 
"A  "  strain  established.     (See  Chart  5,  page  60.) 

Result :  Four  ticks  fed  as  nymphs  on  Hayes  Strain  Guinea 
Pig  19  proved  to  have  transmitted  the  virus  of  Rocky  Moun- 
tain spotted  fever. 

HI.  On  August  5,  1918,  placed  five  female  ticks  of  this 
series  in  a  wire  gauze  capsule  upon  a  normal  rabbit  (white  and 
black),  subsequently  recorded  as  Hayes  Tick  Rabbit  i. 

Record  of  Hayes  Tick  Rabbit  i.  Temperatures:  August  5,  102.2, 
attached  ticks;  August  6,  102.2,  all  ticks  are  feeding;  August  7,  103, 
feces  in  capsule;  August  8,  102.4;  August  9,  103.4;  August  10,  105.7, 
removed  ticks;  all  have  fed  well  (average  size  5x6x2  mm.);  August  11, 
105.4,  scrotum  injected  and  slightly  swollen;  August  13,  105.2;  August 
14,  105.4;   August  15,  104.2,  killed. 

The  autopsy  showed  enlarged  and  pink  inguinal  lymph  nodes,  the 
spleen  deep  red  in  color  and  moderately  enlarged,  and  the  testes  injected. 
All  other  tissues  were  negative.  Microscopic  examination  of  the  tissues 
showed  the  typical  vascular  lesions  of  spotted  fever  in  the  testes  and  skin 
of  the  scrotum,  and  the  parasites  were  found  in  these  lesions. 

Result:  Five  ticks  fed  as  nymphs  on  Hayes  Guinea  Pig  19 
proved  to  have  transmitted  the  virus  of  Rocky  Mountain 
spotted  fever. 

IV.  December  19,  191 8,  placed  two  female  ticks  of  this 
series,  which  had  also  fed  on  Hayes  Tick  Rabbit  i,  on  a  normal 
guinea-pig  which  was  recorded  as  Hayes  Tick  Guinea  Pig  of 
December,  1918. 

Record  of  Hayes  Tick  Guinea  Pig  of  December,  1918.  Temperatures: 
December  19,  ticks  attached;  December  20,  103.8;  December  23,  .101.6; 
December  24,  102.6,  removed  ticks  which  had  fed  sufficiently  to  fill  out 


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ROCKY   MOUNTAIN    SPOTTED    FEVER.  IO7 

the  wrinkles  and  pass  feces;    December  26,  103.6;    December  27,  105.2; 
December  28,  106.4,  killed. 

The  autopsy  showed  typical  lesions  of  spotted  fever  and  from  this 
guinea-pig  the  strain  was  maintained  for  eleven  generations.  (See  Chart 
5,  page  60.) 

Result:  Two  ticks  fed  as  nymphs  on  Hayes  Strain  Guinea 
Pig  19  and  again  upon  a  normal  rabbit  were  proved  to  have 
transmitted  the  virus  of  Rocky  Mountain  spotted  fever. 

Summary  of  conditions  affecting  the  preceding  Table  I. — 
Seven  nymphs  from  the  same  source  fed  on  a  normal  guinea- 
pig  did  not  infect.  (See  first  control  series,  Table  II.)  Of 
ticks  raised  from  one  hundred  and  forty  nymphs  fed  on  Hayes 
Guinea  Pig  19,  three  separate  lots  of  six,  four  and  five  respec- 
tively transmitted  the  virus  of  Rocky  Mountain  spotted  fever, 
and  in  a  fourth  experiment  two  ticks  of  the  five  used  to  infect 
a  rabbit  also  infected  a  guinea-pig.  It  seems  reasonable  to 
■conclude  that  the  majority  or  all  of  the  ticks  fed  as  nymphs  on 
Hayes  Guinea  Pig  19  contained  the  virus  of  Rocky  Mountain 
spotted  fever. 

Summary  of  results  in  Table  I.  —  Forty-five  nymphs  fed 
■on  Hayes  strain  Guinea  Pig  19  were  dissected  and  examined 
for  the  parasite  of  Rocky  Mountain  spotted  fever  during  a 
period  of  forty-seven  days  extending  from  the  first  day  after 
■dropping  as  fully  engorged  nymphs  through  and  into  the 
adult  stage.  The  smear  preparation  technic  was  controlled 
by  selecting  at  random  ticks  throughout  the  series  for  serial 
sectioning. 

The  parasites  were  found  on  and  after  the  fifth  day  (note 
influence  of  temperature  in  chart)  with  but  one  exception 
(Tick  LXXXVL). 

The  first  form  to  appear  in  smears  of  the  gut  is  the  relatively 
large  pale-blue  staining  rod.  at  which  time  the  minute  intra- 
nuclear forms  may  be  found  in  sections  of  the  rectal  sac  and 
intestines. 

In  the  early  stages  of  digestion  in  the  nymph  many  confusing 
bodies  are  found,  free  and  within  cells  of  the  intestinal  tract. 
For  a  while,  tiny  red  and  blue  stained  bodies,  one  or  two 


I08  WOLBACH. 

microns  in  diameter,  massed  in  epithelial  cells  of  the  intestine, 
were  given  consideration  as  possible  parasitic  forms,  as  their 
resemblance  to  Theileria  was  rather  striking.  However,  these 
forms  in  later  stages  of  digestion  lost  their  red  and  blue 
staining  and  many  became  pigmented  greenish.  A  study 
of  the  control  nymphs  showed  the  presence  of  these  bodies 
in  equal  abundance,  thereby  absolutely  disproving  relation- 
ship to  the  parasite  of  Rocky  Mountain  spotted  fever.  As 
digestion  in  the  tick  is  wholly  intracellular,  the  most  plausible 
explanation  of  these  bodies,  and  one  supported  by  considerable 
morphological  evidence,  is  that  they  are  derived  from  the 
nuclei  of  ingested  white  blood  corpuscles. 

With  the  appearance  in  the  intestine  of  the  minute  rods 
with  chromatoid  granules,  the  large  forms  diminish  in  num- 
bers and  finally  disappear  (eight  to  fifteen  days,  according  to 
temperature).  Still  later  the  densely  staining  lanceolate 
forms  appear  in  the  intestines;  from  about  the  sixteenth  day 
on.  The  period  of  greatest  abundance  of  the  minute  rods 
with  chromatoid  granules  in  smears  of  the  intestinal  tract 
corresponds  with  the  greatest  abundance  of  intranuclear 
forms  in  sections.  Lanceolate  forms,  however,  can  be  found 
in  sections  in  most  organs  immediately  after  the  intranuclear 
forms  make  their  appearance. 

Since  the  lanceolate  is  the  only  form  that  caii  be  demon- 
strated in  the  blood  of  infected  mammals,  it  is  probably  the 
one  introduced  into  the  tick.  From  this  densely  staining 
lanceolate  form  must  come  the  pale-blue  staining  rods  which 
are  the  first  indication  of  multiplication  of  a  specific  parasite 
in  infective  ticks.  The  period  of  greatest  abundance  of  the 
parasite  in  the  tick  is  that  coincident  with  the  greatest  intra- 
nuclear development,  and  the  minute  rods  with  chromatoid 
dots.  The  lanceolate  form  is  a  late  arrival  in  the  tick,  and 
represents  the  completion  of  a  fairly  definite  morphological 
cycle,  and  as  the  lanceolate  form  only  can  be  demonstrated 
in  the  salivary  gland  cells  and  ducts  of  both  types  of  salivary 
gland  acini  in  the  tick,  it  is  reasonable  to  suppose  that  the 
parasite  is  reintroduced  into  mammals  in  this  form. 


ROCKY   MOUNTAIN    SPOTTED    FEVER. 


109 


Confirmatory  evidence  of  this  last  theory  is  the  fact  that 
the  lanceolate  paired  forms  were  found  in  large  numbers  in 
mononuclear  phagocytic  cells  (endothelial  cells)  in  sections 
through  a  tick  bite  made  in  infecting  Hayes  Strain  Guinea 
Pig  3. 

(3)  Control  ticks.  Nymphs  proved  non-infective.  First 
series.  —  These  nymphs  were  raised  by  Dr.  W.  V.  King  from 
eggs  in  July,  1916,  in  Victor,  Mont.  They  were  fed  on  a 
normal  male  Guinea  Pig  6,  August  4  to  13,  1917,  when  seven 
fully  engorged  nymphs  were  recovered,  which  had  dropped 
from  the  guinea-pig. 

Temperatures  of  normal  Guinea  Pig  6  after  removal  of  the  nymphs: 
August  13,  102.4;  August  14,  102.5;  August  15,  102;  August  16,  101.4; 
August  17,  loi;  August  18,  102;  August  19,  20,  lOi;  August  21,  100; 
August  22,  loi;   August  23,  102.4;   August  24,  101.6;  August  25,  loi. 

This  guinea-pig  was  not  tested  for  susceptibility,  as  it  died 
on  August  27,  together  with  several  others,  from  the  effects 
of  an  exclusive  cabbage  diet. 

Table  II. 


No.  of  Tick. 


Date  Dissected,  Time  after  Dropping, 
Temperature  Conditions. 


Smears    of    Gut 

and  Malpighian 

Tubes. 


Serial  Sections, 
All  Tissues. 


CIV.  . 
CVI.  . 

evil.. 

CVIII. 
CIX.  . 
CXIV. 

CXIX. 


August  16,  3  days  at  37.5°  C.  in  incuba- 
tor. 

August  17,  4  days  at  37.5°  C. 

August  20,  7  days  at  37.5°  C. 

August  20,  7  days  at  37.5°  C. 

August  22,  9  days  at  room  temperature. 

August  23,  9  davs  at  room  temperature; 
I  day  at  37.5°  C. 

August  27,  9  days  at  room  temperature; 
5  days  at  37.5°  C. 


Negative. 

Negative. 
Negative. 
Negative. 
Negative. 
Negative. 

Negative. 


Negative. 
Negative. 
Negative. 
Negative. 


Summary.  —  None  of  this  series  of  seven  nymphs  fed  upon 
a  normal  guinea-pig  and  dissected  over  a  period  of  fourteen 
days,  contained  microorganisms.     The  source  of  these  nymphs 


no 


WOLBACH. 


was  the  same  as  those  fed  upon  Hayes  Strain  Guinea  Pig  19 
(Table  I.). 

(4)  Control  ticks.  Nymphs  proved  non-infective.  Second 
series.  —  These  ticks  were  sent  by  W.  V.  King  as  engorged 
larvae  which  dropped  between  July  26  and  July  27,  191 7. 
They  molted  in  Boston  between  August  6  and  August  13,  1917. 
The  nymphs  were  fed  August  13  to  August  21,  191 7,  on  normal 
female  Guinea  Pig  7.  Seventy-six  fully  engorged  nymphs 
were  collected  which  had  dropped  from  the  guinea-pig. 

Table  III. 


No.  of  Tick. 

Date  Dissected,  Time  after  Dropping, 
Temperature  Conditions. 

Result: 

Smears  of  Gut 

and  Malpighian 

Tubes. 

Serial  Sections, 
All  Tissues. 

ex.   .  .  , 

August  22,  -I  day  at  37.5°  C. 

Negative. 

CXIII.  .    . 

August  23,  2  days  at  37.5°  C. 

Negative. 

Negative. 

CXVI.    .    . 

August  24,  3  days  at  37.5°  C. 

Negative. 

CXVII.      . 

August  25,  4  days  at  37.5°  C. 

Negative. 

cxx.    .  . 

August  27,  6  days  at  37.5°  C 

Negative. 

CXXIII.    . 

August  28,  7  days  at  37.5°  C. 

Negative. 

Negative. 

cxxv.     . 

August  29,  8  days  at  37.5°  C. 

Negative. 

Negative. 

CXXVII.  . 

September  i,  11  days  at  37.5°  C.     Male 
imago,  almost  mature. 

Negative. 

CXXIX.    . 

September  i,  11  days  at  room  tempera- 
ture. 

Negative. 

Negative. 

CXXX.      . 

September  I,  7  days  at  room  tempera- 
ture; 4  days  at  37.5°  C. 

Negative. 

Negative. 

CXXXIII. 

September  4,  14  days  at  room  tempera- 
ture. 

Negative. 

Negative. 

CXXXIV. 

September  4,  female  imago.     7  days  at 
room  temperature;   7  days  at  37.5°  C. 

Negative. 

Negative. 

Temperatures  of  Guinea  Pig  7  after  removal  of  the  ticks:  August  28, 
100;  August  29,  100.8;  August  30,  100.6;  August  31,  102.6;  September 
I,  101.6;  September  3,  102;  September  4,  101.6;  September  5,  101.4; 
September  6,  102;    September  7,  101.2. 

On  September  7  this  guinea-pig  was  inoculated  from  Guinea  Pig  107, 
California  strain. 


ROCKY   MOUNTAIN    SPOTTED   FEVER.  HI 

Temperatures  after  inoculation:  September  8,  102.2;  September  g^ 
10,  102.6;  September  11,  105;  September  12,  106;  September  13,  105.8; 
September  14,  105. 

September  15,  found  dead.  Autopsy  showed  lesions  consistent  in  a 
female  guinea-pig  with  spotted  fever. 

Summary.  —  None  of  this  series  of  twelve  nymphs,  dis- 
sected over  a  period  of  fourteen  days,  contained  microorgan- 
isms. 

(5)  Adult  control  ticks  proved  non-infective.  —  Tick  III., 
9  ,  D.  venustus,  from  Prof.  R.  A.  Cooley;   fed  June  23  to  26, 
1916,  on  normal  male  Guinea  Pig  i.     Dissected  July  3,  1916; 
examined  by  serial  sections.     Result  negative. 

Temperature  of  Guinea  Pig  i,  after  removal  of  tick:  June  26,  104; 
June  27,  102.8;  June  28,  102. i;  June  29,  loi;  June  30,  101.4;  July  i, 
102.2. 

Killed  July  i,  1916.     No  lesions  found. 

Tick  v.,  9  ,  D.  venustus,  from  Prof.  R.  A.  Cooley.  Fed 
June  23  to  26,  191 6,  on  normal  male  Guinea  Pig  2.  Dissected 
July  II,  1916.     Examined  by  serial  sections.     Result  negative. 

Temperature  of  Guinea  Pig  2,  after  removal  of  ticks:  June  26,  103; 
June  2^,  102.4;  June  28,  101.8;  June  29,  102;  June  30,  102. i;  July  i, 
101.9. 

On  July  8,  1916,  this  guinea-pig  was  inoculated  from  Guinea  Pig  158, 
Strain  I.,  and  was  No.  165.  • 

Temperatures:  July  8,  102;  July  9,  102.8;  July  10,  11,  104;  July  12, 
104.6. 

Killed  July  12,  1916.     Autopsy  showed  lesions  typical  of  spotted  fever. 

Tick  VIII.,  9  ,  D.  venustus,  from  Prof.  R.  A.  Cooley,  Fed 
June  23  to  26,  1916,  on  normal  male  Guinea  Pig  2  (see  above). 
Dissected  July  10,  1916.  Examined  by  smears.  Result 
negative. 

Tick  XXII.,  9  ,  D.  venustus,  partly  engorged;  from  Prof. 
R.  A.  Cooley.  Fed  June  23  to  26,  1916,  on  normal  male 
Guinea  Pig  3.  Dissected  July  25,  1916.  Examined  by 
smears  and  serial  sections.     Result  negative. 

Temperature  of  Guinea  Pig  3:  June  26,  loi;  June  27,  102.4;  June  28, 
101.6;   June  29,  102;   June  30,  101.9;   July  I,  101.8. 

July  8,  this  guinea-pig  was  inoculated  from  Guinea  Pig  158,  Strain  I., 
and  proved  susceptible.     Record  lost. 


112  WOLBACH. 

Tick  XXIII.,  9  ,  D.  venustiis,  partly  engorged;  from  Prof: 
R.  A.  Cooley.  Fed  Julj^  13  to  17,  1916,  on  normal  male 
Guinea  Pig  4.  Dissected  August  3,  1916.  Examined  by 
smears  and  serial  sections.     Result  negative. 

Temperatures  of  Guinea  Pig  4  after  removal  of  ticks:  July  18,  102.6; 
July  19,  102;  July  20,  102.8;  July  21,  100.6;  July  22,  103;  July  24,  102. i; 
July  25,  102.2;  July  26,  102;  July  27,  101.4. 

July  27,  this  guinea-pig  was  inoculated  from  Guinea  Pig  42,  Strain  II., 
and  numbered  44. 

Temperatures:  July  28,  ior.4;  July  29,  102;  July  30,  102.6;  July  31, 
106;  August  I,  105.4;    August  2,  105;  August  3,  106. 

Killed.  Autopsy  showed  typical  lesions  of  spotted  fever,  and  inocula- 
tions of  heart's  blood  into  Guinea  Pigs  46  and  47,  Strain  II.,  reproduced 
the  disease  in  both  in  typical  form. 

Tick  XXV.,  D.  venustus,  from  Prof.  R.  A.  Cooley.  Fed 
June  23  to  26,  1 91 6,  on  normal  Guinea  Pig  i  and  again  July 
13  to  17,  1916,  on  normal  male  Guinea  Pig  5.  Dissected 
August  7,  191 6.  Examined  by  serial  sections.  Result  nega- 
tive. 

Temperature  of  Guinea  Pig  5  after  removal  of  ticks:  July  18,  102; 
July  19,  101.2;  July  20,  102.9;  July  21,  100. i;  July  22,  102. i;  July  23, 
;24,  101.6;    July  25,  101.2;    July  26,  101.4;    July  27,  101.3. 

July  27  inoculated  from  Guinea  Pig  173,  Strain  I.,  and  numbered  178. 

Temperatures:  July  27,  101.3;  July  28,  103.2;  July  29,  105.8;  July 
30,  105.8;   July  31,  105.6;   August  I,  105.2;   August  2,  105. 

Killed.     Autopsy  showed  typical  lesions  of  spotted  fever. 

Summary.  —  Six  proved  non-infective  adult  ticks  contained 
no  microorganisms  similar  to  the  parasite  of  Rocky  Mountain 
spotted  fever. 

(6)  Adult  control  ticks  not  tested  (Table  IV.).  — Lot  773, 
unfed  adult  ticks  collected  April  19,  1917,  by  Dr.  W.  V.  King 
by  dragging  along  O'Brien  Creek,  a  tributary  of  the  Bitter 
Root  River.  These  ticks  were  studied  from  sections  only  and 
were  dissected  in  Montana  during  April  and  May,  1917.  In 
the  column  of  results  the  reason  for  mentioning  the  rectal  sac  — 
gut  junction  —  is  that  this  is  the  place  where  intranuclear 
forms  of  the  parasites  are  most  common  in  infected  ticks. 


ROCKY    MOUNTAIN    SPOTTED    FEVER. 
Table  IV. 


113 


No. 

Description. 

Result. 

I 

d"     . 

Negative.     All  tissues,  including  rectal  sac  —  gut  junction. 

2 

9 

Negative,  all  tissues.     Rectal  sac  not  found. 

3 

9 

Negative,  all  tissues,  including  rectal  sac  —  gut  junction. 

4 

9 

Large,  slender,  purple-staining  bacilli  in  all  tissues  except 
brain,  salivary  glands  and  Malpighian  tubes.  Most  abun- 
dant in  the  ova.  Negative  for  organisms  the  size  of  the 
spotted  fever  organism.  Rectal  sac  —  gut  junction  —  nega- 
tive. 

5 

9 

Small  bacilli,  slightly  larger  than  the  spotted  fever  organisms, 
are  present  in  the  ova  and  in  the  epithelial  cells  of  the  gut. 
All  other  tissues  are  negative,  including  rectal  sac  —  gut 
junction. 

6 

c^ 

Negative,  all  tissues,  including  rectal  sac. 

7 

9 

Negative,  all  tissues;  rectal  sac  not  found. 

8 

^ 

Negative,  all  tissues,  including  rectal  sac  —  gut  junction. 

9 

c^ 

In  gut  contents  are  groups  of  minute  bacilli,  but  slightly 
larger  than  the  spotted  fever  organisms.  All  other  tissues 
are  negative,  including  rectal  sac  —  gut  junction. 

10 

c? 

Large,  slender  bacilli,  similar  to  those  in  Tick  IV.,  are  present 
in  all  tissues,  including  testes.  No  organisms  of  the  size  of 
the  spotted  fever  organism  found.  The  rectal  sac  —  gut 
valve  —  was  found. 

II 

9 

All  tissues  negative;  rectal  sac  not  found. 

Lot  772,  adult  ticks  in  various  stages  of  engorgement  col- 
lected April  24,  191 7,  from  cattle,  by  W.  V.  King,  in  O'Brien 
Creek,  Mont.  Dissected  in  Montana  during  April  and  May, 
191 7.     (Table  V.) 

Table  V. 


No. 

Description. 

Result. 

I 
2 

9  about  f  engorged. 

Unengorged  tick.    Sex 
organs  not  in  sec- 
tions. 

All  tissues  negative.     Rectal  sac  not  found. 

A  few  large,   purple-staining  bacilli  in  gut.     Brain, 
salivary  gland,  muscle  and  Malpighian  tubes  nega- 
tive.    No  organisms  of  the  size  of  the  spotted  fever 
organisms  found.     Rectal  sac  not  found'. 

114 


WOLBACH. 
Table  V. —  Continued. 


No. 


Description. 


Result. 


9 
10 


?  about  \  engorged. 
9  about  \  engorged. 

9  about  \  engorged. 

9  almost  fully  en- 
gorged with  ripe 
ova. 

9  apparently  unfed. 

9  has  fed  slightly. 

cf  unengorged. 
c?  unengorged. 


d^  unengorged. 


Negative,  all  tissues.     Rectal  sac  not  found. 

Negative,  all  tissues,  including  rectal  sac  —  gut  junc- 
tion. 

Negative, all  tissues, including  rectal  sac — gut  junction. 

Negative,  all  tissues,  rectal  sac  —  gut  junction  —  not 
found. 


Negative,  all  tissues,  rectal  sac 
found. 


gut  junction  —  not 


Negative,  all  tissues;  rectal  sac  not  found.  In  the 
hypoderm  are  medium-sized  micrococci. 

Negative,  all  tissues,  but  rectal  sac  not  found. 

Large  and  very  minute  bacilli  in  one  diverticulum  in 
an  epithelial  cell.  The  smaller  bacilli  are  equal  in 
size  to  the  spotted  fever  organism.  All  other 
tissues  are  negative,  but  rectal  sac  —  gut  valve  — 
not  found. 

Clumps  of  minute  paired  organisms,  not  distinguish- 
able with  certainty  from  the  spotted  fever  organ- 
ism, are  present  in  epithelial  cells  of  the  diverticu- 
lae.  Rectal  sac  —  gut  valve  —  not  found.  All  other 
tissues  are  negative. 


Summary.  —  Of  eleven  unfed  adult  ticks  dissected  soon 
after  taking  from  their  habitat,  four  contained  bacilli;  in 
two  instances,  of  large  size  and  generally  distributed ;  in  two 
instances,  of  small  size  and  restricted  to  the  gut.  In  no 
instance  were  organisms-  present  which  could  be  confused 
with  the  spotted  fever  organism.  No  intranuclear  micro- 
organisms were  found  in  any  instance. 

In  eleven  ticks  taken  from  cattle  and  dissected  soon  after, 
three  contained  bacilli;  one  micrococci.  The  bacilli  in  all 
instances  were  confined  to  the  gut,  though  in  one  instance 
because  of  their  small  size  confusion  with  the  spotted  fever 
organism  was  possible,  and  possibly  this  was  in  reality  an 
infected  tick.  No  intranuclear  microorganisms  were  found 
in  any  instance. 

In  the  two  series,  totaling  twenty-two  ticks,  none  were 
found  with  a  general  invasion  of  the  tissues  with  organisms 


ROCKY  MOUNTAIN    SPOTTED   FEVER.  II5 

resembling  the  spotted  fever  organisms.  In  two  instances 
only  (in  the  ticks  of  Lot  773)  large,  slender  bacilli  were  found 
in  all  tissues.  The  presence  of  small  bacilli  restricted  to  the 
gut  in  no  way  simulates  the  appearances  present  in  infected 
ticks. 

XIV.       PROPERTIES    OF    THE   VIRUS. 

1.  Filterability.  —  The  protocols  of  experiments  published 
by  Ricketts^^  indicate  conclusively  that  the  virus  in  the  blood 
of  infected  animals  and  in  the  eggs  of  infected  ticks  will  not 
pass  through  Berkefeld  filters.  I  have  not  thought  it  neces- 
sary to  repeat  these  experiments,  but  consider  it  advisable 
to  repeat  filtration  experiments  with  the  tissues  of  infected 
ticks,  as  it  is  possible  that  the  minute  intranuclear  forms  of 
the  parasite  may  prove  filterable. 

Preliminary  transmission  experiments  made  with  thoroughly 
crushed  tissues  from  proved  infective  ticks  have  deterred 
me  from  attempting  filtration  experiment,  as  uncertain  results 
were  obtained  with  the  unfiltered  crushed  tissues  suspended 
in  salt  solution.  The  cause  of  failure  to  infect  animals  by 
tick  tissues  so  treated  has  not  been  ascertained.  In  these 
experiments,  using  proved  infective  ticks,  it  was  not  possible 
to  transmit  the  disease  by  injecting  the  thoroughly  crushed 
tissues  suspended  in  salt  solution,  and  I  have  arrived  at  the 
tentative  conclusion  that  the  infectivity  of  the  virus  was 
destroyed  by  the  procedure. 

2.  Resistance  to  glycerine.  ■ —  Portions  of  testis,  liver,  spleen 
and  kidney  of  infected  guinea-pigs  were  placed  in  a  large  excess 
of  twenty-five  per  cent  and  fifty  per  cent  glycerine  (Merck's 
reagent)  in  distilled  water  and  stored  in  the  ice-chest  7°  C.  to 
10°  C.  until  tested  for  infectivity.  The  material  before  in- 
jection was  washed  in  several  changes  of  sterile  .8  per  cent 
salt  solution  and  then  ground  in  a  mortar,  and  suspended 
in  salt  solution  for  injection  into  guinea-pigs.  The  suspen- 
sions were  always  injected  intraperitoneally.  The  amount 
of  tissue  actually  injected  into  each  guinea-pig  used  for  the 
tests  was  estimated  as  equal  to  1.5  to  2.0  grams  of  fresh  tissue. 


Il6  WOLBACH. 

Destruction  of  the  virus  was  considered  as  proved  if  the 
guinea-pig  did  not  develop  spotted  fever. 

The  results  of  these  experiments  are  fragmentary,  owing 
to  the  loss  of  several  guinea-pigs  from  epizootic  infections. 

However,  the  emulsions  of  tissues  treated  as  above  con- 
veyed the  disease  to  guinea-pigs  after  one-day  and  five-day 
periods  in  both  twenty-five  per  cent  and  fifty  per  cent  glycerine. 
After  a  period  of  one  month  the  virus  was  destroyed;  inter- 
mediate periods  were  not  tested,  and  the  only  conclusion  per- 
missible is  that  the  virus  has  no  marked  degree  of  resistance  to 
glycerine  such  as  is  possessed  by  the  viruses  of  rabies,  polio- 
myelitis and  smallpox. 

3.  Resistance  to  bile.  —  In  the  following  experiments  ox- 
bile  sterilized  by  heat  (100°  C.)  was  used.  The  blood  from  the 
infected  guinea-pigs  was  drawn  directly  into  an  equal  amount 
of  bile  previously  placed  in  the  syringe.  Three  of  five  guinea- 
pigs  injected  with  mixtures  of  the  bile  and  blood  died  of 
peritonitis.     The  protocols  of  two  that  survived  are  as  follows: 

Experiment  I.  —  .75  c.c.  of  blood  from  California  Strain  Guinea  Pig 
113  drawn  into  an  equal  quantity  of  bile  at  12.10  p.m.,  September  28, 
1917,  and  kept  at  room  temperature  for  three  hours,  and  at  10°  C.  for 
twenty  hours  (total  of  twenty-three  hours),  was  injected  at  11. 10  P.M. 
intraperitoneally  into  a  normal  guinea-pig,  September  29,  19 17.  This 
guinea-pig  remained  normal  and  later  proved  susceptible  to  an  inoculation 
from  Hayes  Strain  Guinea  Pig  56. 

Experiment  II.  — The  source  of  the  virus  was  California  Strain  Guinea 
Pig  116.  The  dose  was  i  c.c.  of  the  bile  blood  mixture;  time,  three  hours 
at  room  temperature.     Result:     Spotted  fever  in  the  test  guinea-pig. 

Results:  The  virus  in  blood  mixed  with  an  equal  quantity 
of  heated  ox-bile  remained  infective  for  three  hours,  but  was 
destroyed  in  twenty-three  hours  (twenty  hours  of  which  were 
at  low  temperature.) 

4.  Resistance  to  dessication.  —  Ricketts"  found  that  the 
virus  was  destroyed  some  time  between  twenty-four  and  forty- 
eight  hours  after  complete  dessication.  In  his  experiments 
the  blood  was  dried  in  Petri  dishes  over  sulphuric  acid  in  a 
dessicator.  For  complete  dessication  eighteen  to  twenty-four 
hours  was  required. 


ROCKY   MOUNTAIN    SPOTTED   FEVER.  II7 

In  the  following  tests  the  blood  was  rapidly  dried  in  open 
Petri  dishes  by  directing  a  current  of  air  upon  it  from  an 
electric  fan.  The  dried  blood  was  then  placed  in  a  dessicator 
over  concentrated  sulphuric  acid  and  the  air  exhausted.  The 
entire  process  required  two  hours.  The  dessicator  containing 
the  blood  was  kept  at  room  temperature  in  diffuse  daylight. 

The  blood  was  tested  by  triturating  the  dried  blood  with 
.8  per  cent  salt  solution  and  injecting  into  guinea-pigs. 

Experiment  I. —  1.2  c.c.  of  blood  drawn  from  Hayes  Strain  Guinea 
Pig  22  at  3.00  P.M.,  July  13,  1917,  and  treated  as  above,  was  injected  into 
a  guinea-pig  intraperitoneally  July  14,  1917,  at  10.45  P-^i-  (The  dosage 
was  actually  equal  to  less  than  the  amount  withdrawn  and  probably  .5 
to  .7  c.c.) 

This  guinea-pig  remained  normal  and  was  subsequently  proved  sus- 
ceptible to  inoculation  with  blood  from  California  Strain  Guinea  Pig  97. 

Result:  Estimating  the  time  of  dessication  at  two  hours, 
the  virus  was  destroyed  in  fifteen  hours,  forty-five  minutes. 

Experiment  II.  —  i  c.c.  of  blood  drawn  from  Hayes  Strain  Guinea  Pig 
31  at  1 1. 15  A.M.,  July  25,  1917,  and  treated  as  above,  was  injected  into  a 
guinea-pig  intraperitoneally  July  26,  1917,  at  12.00  m.  o'clock.  (The 
dosage  included  the  whole  amount  of  blood  drawn.) 

This  guinea-pig  remained  normal  and  was  subsequently  proved  sus- 
ceptible to  inoculation  with  blood  from  California  Strain  Guinea  Pig  97. 

Result:  Estimating  the  time  of  dessication  at  two  hours, 
the  virus  was  destroyed  in  ten  hours,  forty-five  minutes. 

5.  Preservation  in  defibrinated  and  citrated  blood.  —  In 
these  tests  the  blood  was  defibrinated  immediately  after  with- 
drawing it  from  the  heart  of  infected  guinea-pigs,  by  means 
of  a  syringe  fitted  with  a  large-sized  needle.  The  infectivity 
was  tested  by  injection  into  normal  guinea-pigs.  At  room 
temperature  at  the  end  of  five  days  0.5  cubic  centimeters, 
injected  intraperitoneally,  infected  guinea-pigs  with  spotted 
fever.  Kept  in  the  cold  room  at  7°  C.  to  10°  C.  for  twelve 
days  one  cubic  centimeter  infected  guinea-pigs  with  spotted 
fever.  The  incubation  period,  at  the  end  of  five  days  at 
room  temperature,  and  at  the  end  of  twelve  days  in  the  cold 
room,  was  considerably  delayed  in  both  instances;  in  the 
former  instance  it  was  six  days,  in  the  latter  instance  five 
days.     These  experiments  are  incomplete. 


Il8  WOLBACH. 

Ricketts^^  found  that  blood  retained  its  infectiousness  upon 
ice  for  sixteen  days,  although  large  amounts,  five  cubic  centi- 
meters, were  required  to  infect.  He  found  that  blood  which 
would  infect  with  a  dose  of  .i  cubic  centimeter  when  drawn, 
in  eleven  days  required  two  cubic  centimeters  to  infect.  In 
one  experiment,  at  the  end  of  fifteen  days  upon  ice,  a  dose 
of  three  cubic  centimeters  failed  to  infect. 

Blood  from  infected  animals  drawn  into  equal  parts  of 
citrate  saline  solution  (one  per  cent  sodium  citrate  in  .8  per 
cent  sodium  chloride  solution),  and  kept  in  the  cold  room  at 
10°  C,  in  doses  of  2  to  2.5  cubic  centimeters  of  the  mixture, 
failed  to  infect  at  the  end  of  twenty-eight  days.  The  blood 
from  rats  infected  with  African  relapsing  fever  remained  in- 
fectious under  the  same  conditions  for  forty  days.  At  room 
temperature  the  virus  is  destroyed  in  citrated  blood  in  six  to 
eight  days. 

6.  Resistance  to  heat.  —  Ricketts  found  that  the  virus  was 
not  destroyed  when  heated  at  45°  C.  for  thirty  minutes;  but 
was  destroyed  in  twenty-five  minutes  at  50°  C. 

In  our  own  tests  the  following  technic  was  employed. 
Blood  from  infected  guinea-pigs  was  defibrinated  and  mixed 
with  an  equal  part  of  .8  per  cent  salt  solution,  and  divided 
into  quantities  of  two  cubic  centimeters,  which  were  sealed  in 
glass  ampules.  The  ampules  were  completely  submerged  for 
the  tests,  in  a  water  bath  kept  at  the  desired  temperature. 
One  ampule  in  each  experiment  similarly  filled  was  fitted 
with  a  thermometer  and  the  period  of  the  experiment  was 
recorded  from  the  instant  the  desired  temperature  was  reached. 
The  ampules  were  plunged  into  cold  water  at  the  end  of  the 
test.  The  infectivity  of  the  blood  at  the  end  of  the  experiment 
was  determined  by  injecting  one  or  two  cubic  centimeters  of 
the  mixture  intraperitoneally  into  a  normal  guinea-pig.  In 
each  instance  where  the  guinea-pig  did  not  acquire  the  disease, 
it  was  proved  susceptible  by  a  subsequent  inoculation  with 
blood  from  another  infected  guinea-pig. 

The  results  are  recorded  in  the  following  table. 


ROCKY    MOUNTAIN    SPOTTED    TEVER. 
Table  VI. 


119 


Source  of  Virus. 

Temperature. 

Time. 

Result. 

Remarks. 

Hayes  Guinea  Pig  31    . 

55=  C. 

15  minutes. 

Destroyed. 

Dose  I  c.c. 

Hayes  Guinea  Pig  31    . 

55°  C. 

5  minutes. 

Destroyed. 

Dose  I  c.c. 

Hayes  Guinea  Pig  71    . 

55°  C. 

5  minutes. 

Destroyed. 

Dose  I  c.c. 

Calif.  Guinea  Pig  133  . 

50°  c. 

15  minutes. 

Destroyed. 

Dose  I  c.c. 

Calif.  Guinea  Pig  134  . 

50°  C. 

5  minutes. 

Destroyed. 

Dose  I  c.c. 

Hayes  Guinea  Pig  47    . 

49°  C. 

15  minutes. 

Destroyed. 

Dose  2  c.c. 

Hayes  Guinea  Pig  47    . 

49°  C. 

10  minutes. 

Destroyed. 

Dose  2  c.c. 

Hayes  Guinea  Pig  47    . 

49°  C. 

5  minutes. 

Not  destroyed. 

Dose  2  c.c. 

Hayes  Guinea  Pig  46    . 

45°  C. 

15  minutes. 

Not  destroyed. 

Dose  2  c.c. 

Calif.  Guinea  Pig  127  . 

45°  C. 

15  minutes. 

Not  destroyed. 

Dose  2  c.c. 

Calif.  Guinea  Pig  127  . 

45°  C. 

10  minutes. 

Not  destroyed. 

Dose  2  c.c. 

Hayes  Guinea  Pig  46    . 

45°  C. 

10  minutes. 

Not  destroyed. 

Dose  2  c.c. 

Hayes  Guinea  Pig  46    . 

45°  C. 

5  minutes. 

Not  destroyed. 

Dose  2  c.c. 

Calif.  Guinea  Pig  131  . 

45°  C. 

15  minutes. 

Not  destroyed. 

Citrated 
blood  used. 
Dose,  1.5 
c.c. 

These  results  show  that  the  virus  will  resist  45°  C.  for 
fifteen  minutes  and  49°  C.  for  five  minutes.  It  is  destroyed 
at  49°  C.  in  ten  minutes  and  at  50°  C,  in  five  minutes.  The 
destructive  temperature  therefore  lies  between  45°  C.  and 
49°  C. 

7.  The  resistance  to  freezing.  —  In  these  tests  equal  parts 
of  blood  from  infected  guinea-pigs  and  citrate  saline  solution 
(.8  per  cent  salt,  i  per  cent  sodium  citrate)  were  frozen  as 
soon  as  possible  by  placing  against  the  refrigerator  coils  in  a 
cold  room.     The  probable  temperature  was  — 1°  to  —3°  C. 

Guinea-pigs  inoculated  at  the  end  of  three  and  four  days' 
freezing  became  infected  with  spotted  fever,  while  those  in- 
oculated at  the  end  of  nine  and  twelve  days  did  not  become 
infected. 


120  WOLBACH. 

This  experiment  indicates  that  the  virus  will  withstand 
freezing  for  a  period  longer  than  four  and  less  than  nine  days. 

XV.       ROCKY     MOUNTAIN     SPOTTED     FEVER     IN     EXPERIMENTAL. 

ANIMALS. 

I.  The  disease  in  guinea-pigs  (Figs.  29,  45,  46,  48,  49,  52,. 
59,  64  and  69.)  —  After  inoculation  of  blood  from  a  strain 
established  in  guinea-pigs,  the  temperature  usually  rises  to 
103°  or  104°  F.  at  the  end  of  forty-eight  or  seventy-two 
hours,  rarely  one  or  two  days  later. 

After  inoculation  of  blood  from  human  cases  the  tempera- 
ture usually  does  not  rise  until  seventy-two  to  ninety-six 
hours  have  passed,  and  in  the  first  few  transfers  to  guinea- 
pigs  the  incubation  period  may  vary  from  three  to  five  days, 
until  it  becomes  fixed-«.t  from  forty-eight  to  seventy-two  hours.. 

The  incubation  period  when  the  disease  is  transmitted  by 
ticks  is  from  three  to  seven  days  after  the  tick  has  attached,, 
the  usual  period  is  four  to  five  days. 

After  the  initial  rise,  the  temperature  quickly  reaches  105°  F. 
to  106°  F.,  usually  on  the  second  or  third  day,  and  a  high 
level,  105°  to  106°  F.,  is  maintained.  Death,  which  usually 
occurs  in  well-established  strains  on  the  sixth  to  seventh  day 
of  fever,  or  eight  or  nine  days  after  inoculation,  is  preceded 
by  a  sudden  drop  of  temperature  to  subnormal.  The  uniform 
course  of  the  disease  in  well-established  strains  in  guinea-pigs 
is  striking,  and  resembles  the  behavior  of  a  fixed  rabies  virus. 

If  the  guinea-pig  is  going  to  recover,  the  temperature  begins 
to  drop  at  the  end  of  seven  or  eight  days,  and  gradually  reaches- 
normal  in  a  period  of  from  three  to  six  days  more.  A  tem- 
perature of  103°  to  103.5°  F.  may  persist  for  a  week  or  ten  days. 

The  first  visible  sign  of  the  disease  in  male  guinea-pigs  is 
the  swelling  and  reddening  of  the  skin  of  the  scrotum,  which 
occurs  on  the  third  to  fourth  day  of  temperature,  at  which 
time  the  animal  begins  to  exhibit  signs  of  discomfort,  loss  of 
appetite  and  roughness  of  coat.  The  skin  of  the  scrotum 
soon  becomes  dull  red,  and  may  exhibit  a  definite  line  of 
demarcation  about  a  necrotic  portion  on  the  sixth  to  seventh. 


ROCKY   MOUNTAIN    SPOTTED    FEVER.  121 

day  of  temperature.  (Fig.  52.)  Reddening  and  swelling  of 
the  eyelids,  ears  and  paws  is  not  seen  as  a  rule  unless  the 
animal  survives  six  or  seven  days  of  temperature.  Necrosis 
of  the  paws  resulting  in  ulcers,  and  of  the  ears  resulting  in 
dry  necrosis  and  separation,  takes  place  on  the  tenth  to 
fourteenth  day,  and  may  not  take  place  until  the  temperature 
is  almost  normal,  or  has  become  fixed  at  103°  to  103.5°  F.  for 
a  period  of  several  days. 

In  female  guinea-pigs  the  reaction  to  the  disease  is  less 
striking,  as  the  tissues  of  the  vulva  and  anus  rarely  show 
lesions  comparable  to  those  of  the  scrotum  in  the  male. 
Ordinarily,  unless  the  animal  lives  long  enough  to  develop 
the  lesions  of  paws  and  ears,  we  must  rely  upon  the  temperature 
for  diagnosis. 

The  post-mortem  findings  vary  with  the  duration  of  the 
disease.  In  male  guinea-pigs  killed  at  the  end  of  five  or  six 
days  of  temperature,  we  find  oedema  and  congestion  of  and 
hemorrhage  into  the  skin  and  subcutaneous  tissues  of  the 
scrotum.  The  vessels  of  the  skin  of  the  whole  surface  of  the 
body  are  finely  injected,  and  this  may  be  seen  by  removing 
the  skin  under  anaesthesia.  Generalized  hemorrhages  do  not 
occur  into  the  skin;  the  scrotum,  paws  and  ears  are  the  only 
sites  of  hemorrhage  and  necrosis  of  the  skin.  The  inguinal 
and,  to  a  less  degree,  the  axillary  lymph  nodes  are  swollen 
and  reddened. 

The  peritoneal  surfaces  and  intestinal  tract  are  normal. 
The  spleen  is  enlarged  to  three  to  five  times  its  normal  size,  is 
dark-red  in  color  and  firm  in  consistency.  There  may  be  a 
very  thin,  translucent  layer  of  fibrin  upon  its  surface.  The 
liver  usually  presents  small  yellow^ish  opaque  areas  of  necrosis 
which  are  common  in  any  infection  in  guinea-pigs,  so  that 
their  significance  is  doubtful.  The  gastro-intestinal  tract  is 
normal.  The  kidneys  are  normal.  The  adrenals  usually 
show  injection  of  the  medulla,  but  hemorrhages  do  not  occur 
in  uncomplicated  cases. 

The  organs  of  the  chest  are  normal. 

The  most  striking  changes  are  found  in  the  testes  and 
adnexa.  The  testes  are  swollen  and  markedly  injected,  usu- 
ally with  minute  hemorrhages  into  the  tunica  at  both  poles. 


122  WOLBACH.  , 

The  polar  fat  is  discolored  and  contains  small  hemorrhages. 
The  cremasteric  muscles  and  parietal  tunica  are  deep  red, 
often  hemorrhagic,  and  both  these  structures  are  adherent  to 
each  other  and  to  the  testes.  Small  hemorrhages  are  practi- 
cally constant  in  the  epididymis,  particularly  between  the 
testis  and  epididymis.  Hemorrhages  into  the  areolar  tissue 
around  the  ductus  deferens  are  the  rule. 

In  late  cases  the  testes  become  adherent  in  the  scrotum, 
•due  to  organization  of  the  necrotic  tissues  and  exudate,  and 
the  subcutaneous  tissues  surrounding  the  anus  and  scrotum 
are  thickened,  brawny  and  hemorrhagic.  The  seminal  vesicles 
are  normal. 

The  central  nervous  system  may  be  injected,  but  shows 
no  lesions.  Dissection  of  the  tendon  sheaths  of  the  feet  in 
late  cases  shows  a  permanent  dusky  red  injection  and  often 
minute  hemorrhages. 

In  female  guinea-pigs  a  marked  injection  of  the  uterus  and 
-ovaries  is  the  rule.  Actual  hemorrhages  are  very  rare.  The 
other  organs  exhibit  the  same  lesions  as  in  the  male. 

Male  guinea-pigs,  because  of  the  characteristic  reaction 
shown  in  the  scrotum,  have  been  used  almost  exclusively  in 
my  own  work;  females  being  employed  only  when  normal 
males  were  not  obtainable. 

Guinea-pigs.  Microscopic.  —  Heart:  The  heart  muscle, 
pericardium,  endocardium,  valves  and  blood  vessels  invariably 
have  no  lesions.  Aorta:  Without  lesions.  Lungs:  The 
lungs  invariably  show  a  strikingly  large  number  of  large 
mononuclear  cells  (endothelial  cells)  in  the  alveolar  capillaries, 
and  cells  in  mitosis  free  and  attached  to  the  capillary  walls 
are  common.  These  mononuclear  cells  are  frequently  phago- 
cytic for  red  blood  cells  and  polymorphonuclear  leucocytes. 
They  are  sometimes  massed  in  great  numbers,  and  occasion- 
ally there  are  collections  of  them  containing  a  rare  multinu- 
cleated cell  in  an  alveolus.  Small  arteries  and  veins  occa- 
sionally contain  collections  of  a  few  similar  mononuclear 
phagocytic  cells  attached  to  the  intima,  but  the  larger  vessels 
are  without  lesions  and  thromboses  are  never  found.     The 


ROCKY   MOUNTAIN    SPOTTED    FEVER.  1 23 

interlobular  lymphatics  may  also  contain  large  numbers  of 
these  large  mononuclear  phagocytic  cells.  The  bronchi  are 
without  lesions. 

Spleen:  Marked  congestion  of  the  sinuses  and  pulp  veins, 
with  a  heavy  accumulation  of  large  mononuclear  (endothelial) 
cells  in  the  blood  spaces  and  in  the  pulp,  are  the  common 
features.  In  late  cases  the  megakaryocytes  and  erythro- 
blasts  and  most  of  the  lymphoid  cells  are  absent  and  the 
reticular  tissue  is  filled  with  endothelial  cells,  many  of  which 
enclose  red  blood  cells  or  polymorphonuclear  leucocytes. 
Mitoses  are  numerous  in  the  meshes  of  the  reticular  tissue, 
and  in  the  pulp  veins  (sinuses)  where  endothelial  cells  remain 
attached  to  the  vessel  walls  while  in  the  act  of  dividing. 
There  is  no  evidence  of  activity  on  the  part  of  the  lymphoid 
tissue  and  in  cases  with  advanced  lesions  the  Malpighian 
bodies  are  recognizable  with  difficulty  because  of  their  small 
size  and  partial  replacement  by  endothelial  cells.  There  are 
no  degenerative  lesions  or  necrosis.  Thromboses  are  absent 
and  the  arteries  and  larger  veins  are  without  lesions.  The 
capsule  and  peritoneal  serosa  are  usually  normal. 

Liver:  The  liver  may  be  normal  except  for  an  increase 
in  large  monocuclear  (endothelial)  cells  in  the  sinusoids  and 
hepatic  veins.  These  cells  while  still  attached  to  the  sinusoid 
walls  contain  red  blood  cells  and  polymorphonuclear  leuco- 
cytes and  fragments  obviously  derived  from  these  elements; 
occasionally  attached  endothelial  cells  are  in  mitosis.  The 
arteries  and  larger  veins  are  free  from  lesions.  The  bile 
passages  are  normal.  In  many  livers  small  necroses  are 
found,  consisting  of  from  one  to  several  vacuolated,  deeply 
staining  liver  cells  with  pyknotic  nuclei  and  invaded  by  poly- 
morphonuclear leucocytes.  Extensive  necroses  are  probably 
attributable  to  other  processes,  as  they  are  not  common  in 
uncomplicated  spotted  fever  in  guinea-pigs.  The  capsule  and 
peritoneal  serosa  are  normal. 

Pancreas:  The  pancreas  is  invariably  normal.  Gastro- 
intestinal tract :  Invariably  normal.  Kidneys:  The  kidneys 
usually  show  an  increase  in  the  number  of  cells  in  the  glo- 
meruli, due  to  the  accumulations  of  mononuclear  (endothelial) 


124  WOLBACH. 

cells  in  the  capillaries.  Mitosis  of  the  capillary  endothelium 
is  of  exceedingly  rare  occurrence.  The  renal  epithelium  shows 
no  lesions.     The  blood  vessels  are  normal. 

Adrenal  gland:  Beyond  a  moderate  injection,  usually 
normal.  Rarely  a  small  necrosis  is  found  in  the  fasicular 
zone  in  the  cortex.  The  blood  vessels  are  normal.  Periph- 
eral lymph  nodes:  The  sinuses  are  distended  from  fluid  con- 
taining many  large  mononuclear  phagocytic  (endothelial) 
cells  containing  mostly  red  blood  cells.  The  reticular  tissue 
also  contains  many  similar  cells.  The  blood  vessels  are  in- 
jected but  show  no  lesions. 

Testes  and  adnexa:  The  seminiferous  tubules  show  de- 
generative changes  to  a  degree  corresponding  with  the  lesions 
present  in  the  blood  vessels.  Cessation  of  spermatogenesis 
is  common,  with  complete  absence  of  the  spermatids.  The 
disappearance  of  the  spermatids  is  preceded  by  a  stage  in 
which  greatly  swollen  cells  of  this  series  are  found  undergoing 
atypical  multipolar  mitotic  division.  The  tubules  of  the  rete 
and  epididymis  rarely  show  lesions  except  where  involved  in 
small  perivascular  necroses.  The  blood  vessels  of  the  inter- 
stitial tissue,  the  tunica,  epididymis,  polar  fat  and  of  the 
cremasteric  muscle  invariably  show  striking  lesions  and  the 
presence  of  the  minute  paired  microorganism  in  the  lesions. 
The  earliest  lesions  consist  of  collections  of  endothelial  cells 
heaped  up  in  situ  in  the  intima  of  arteries  and  veins,  or  filling 
capillaries.  Mitotic  figures  are  common  in  arteries  and  veins 
and  frequently  vessels  of  fair  size  are  completely  occluded  by 
masses  of  endothelial  cells.  These  cells  can  also  be  traced 
in  migration  through  the  media,  whence  they  go  to  form 
compact  zones  in  and  around  the  adventitia;  further  multi- 
plication occurs  in  these  perivascular  accumulations,  as  is 
evidenced  by  numerous  mitoses.  (Figs.  45  and  49.)  Small 
deposits  of  fibrin  are  found  in  arteries  and  veins,  and  occlusion 
may  result  from  this  type  of  thrombosis.  The  infiltration 
of  the  media  with  endothelial  cells  and  polymorphonuclear 
leucocytes  also  leads  to  a  marked  degree  of  concentric  thicken- 
ing and  diminution  of  caliber.  Hyaline  degeneration  and 
necrosis  of  the  smooth  muscle  cells  is  of  invariable  occurrence,. 


ROCKY    MOUNTAIN    SPOTTED    FEVER.  125 

and  frequently  the  original  lumen  of  an  artery  is  indicated 
by  the  deeply  acidophilic  staining  of  the  inner  zone  of  muscle 
cells   (Fig.  45).     In   the  interstitial  tissue  of  the    testis  and 
epididymis   small    veins   and   capillaries    become    filled   with 
endothelial  cells  and   the  connective   tissue  and   lymphatics 
also  acquire  large  numbers  of  them.     These  cells  often  contain 
red  blood  cells,  lymphoid  cells  and  polymorphonuclear  leuco- 
cytes.    Arteries  and  veins,  in  addition  to  fibrin  formation, 
frequently  contain   masses   of  fused    hyaline-appearing    red 
blood    corpusles.     Fairly   extensive    areas   of    necrosis   occur 
in  the  testes,   tunica  and  cremasteric  muscles,  accompanied 
by  the  appearance  of  fibrin,  polymorphonuclear  leucocytes, 
lymphoid    and    plasma   cells   and    eosinophiles.     The    serous 
epithelium  of  the  tunica  is  usually  swollen  and  cuboidal  and 
the  surface  when  adjacent  to  underlying  necroses  becomes 
covered  with  an  exudate  of  fibrin  and  cells.     Organization 
of  this  exudate  occurs  in  late  cases  with  resulting  fusion  of 
the   parietal   and   visceral   tunicae.     In   the   endothelial    cell 
and  in  smooth  muscle  cells  of  arteries  and  veins  with  lesions 
the  minute  paired  microorganism  is  found  in  large  numbers. 
Smooth  muscle  cells  literally  become  packed  with  them,  so 
that  their  presence  enables  the  tracing  of  the  course  of  the 
infected   cells   at   the  branching  of  blood  vessels    (Fig.   69). 
The  parasites  occur  also  in  detached  endothelial  cells  lying 
in  the  lumina  of  vessels  and  less  frequently  can  be  found  in 
the  cells  in  the  perivascular  zones. 

Skin:  The  skin  of  the  scrotum,  anus  and  prepuce  invari- 
ably is  the  seat  of  similar  lesions  of  the  blood  vessels.  (Figs. 
48,  49,  64,  69.)  In  advanced  cases  the  skin  of  the  ears  and  the 
paws  shows  the  lesions.  In  guinea-pigs  the  skin  from  other 
locations  has  not  been  examined.  In  the  skin  the  blood  ves- 
sels show  more  tendency  to  form  fibrin  thrombi,  and  less 
marked  perivascular  zones  of  endothelial  cell  infiltration. 
Secondary  degeneration  and  necrosis  of  the  appendages  of 
the  skin,  hair  follicles  and  glands  is  always  present,  and  often 
extensive  necrosis  and  ulceration  of  the  skin  of  the  scrotum , 
ears  and  paws  result  from  the  obliteration  of  blood  vessels- 
Secondary  infection  of  the  necrotic  skin  produces  the  usual 
microscopic  appearances  of  suppuration. 


126  WOLBACH. 

The  tick  bite:  Microscopic  examination  of  the  seat  of 
the  bite  of  infected  ticks  shows  several  interesting  features. 
The  epidermis  at  the  point  of  attachment  is  absent,  and  the 
surface  of  the  exposed  corium  is  necrotic  and  infiltrated  with 
fibrin  and  leucocytes.  Regeneration  of  the  epidermis  occurs 
at  the  edges,  while  the  tick  is  still  feeding.  Extending  from 
the  surface  into  the  corium  are  diverging  strands  of  fibrin. 
The  corium  is  oedematous,  the  strands  of  collagen  are  widely- 
separated,  and  new  fibroblasts  are  present  in  great  numbers 
in  a  wide  zone  surrounding  the  point  of  attachment  and 
extending  into  the  subcutaneous  tissue  and  even  into  the 
muscle  panniculus.  In  the  central  portion  of  the  lesion  are 
distributed  large  numbers  of  mononuclear  phagocytic  (endo- 
thelial) cells  enclosing  red  corpuscles  and  polymorphonuclear 
leucocytes.  These  endothelial  cells  often  contain  large  num- 
bers of  the  minute  paired  parasites  (Fig.  59).  The  charac- 
teristic endothelial  proliferation  in  blood  vessels  is  present 
after  the  animal  becomes  infected.  In  case  of  recovery  from 
the  infection  the  seat  of  the  tick  bite  leaves  a  dense  plaque  of 
fibrous  tissue  occupying  the  lower  layers  of  the  corium  and 
subcutaneous  tissue.  Control  bites  of  normal  ticks  have  not 
been  studied,  but  it  is  evident  that  the  material  injected  by 
the  feeding  tick  stimulates  a  marked  proliferation  of  fibro- 
blasts.    The  surface  lesion  repairs  by  organization. 

Bone  marrow:  There  are  no  lesions;  normal  activity  is 
invariably  present. 

2.  The  disease  in  rabbits  (Figs.  6  and  7).  —  Unlike  guinea- 
pigs,  the  susceptibility  of  the  rabbit  is  subject  to  vagaries 
which  have  not  yet  been  explained.  The  disease  in  rabbits 
has  recently  been  studied  by  Foot^''  in  my  laboratory.  In 
one  of  two  attempts  the  disease  was  transmitted  to  a  rabbit 
by  ticks  which  were  infected  as  nymphs.     (See  page  99.) 

In  fourteen  inoculations  of  rabbits  with  blood  from  guinea- 
pigs,  ten  developed  the  disease  in  typical  form,  three  gave- 
doubtful  reactions,  and  one  resulted  negatively.  In  eleven 
inoculations  from  rabbits  to  rabbits,  six  were  unmistakably 
positive,  two  were  doubtful  and  three  negative.     Foot  has 


ROCKY    MOUNTAIN    SPOTTED    FEVER.  12/ 

pointed  out  the  impossibility  of  maintaining  the  strain  in 
rabbits  without  alternating  with  guinea-pigs,  but  further  work 
is  necessary  to  discover  the  cause  of  this  difficulty.  It  seems 
probable  that  the  virus  is  present  in  the  blood  for  a  shorter 
time  than  is  the  case  with  man,  monkey  and  guinea-pig. 
That  this  is  the  case  is  supported  by  the  fact  that  it  has  been 
occasionally  impossible  to  infect  guinea-pigs  from  rabbits 
showing  unmistakable  anatomical  and  febrile  evidence  of  the 
disease. 

The  course  of  the  disease  after  successful  inoculation  is 
practically  the  same  in  rabbits  as  in  guinea-pigs,  and  the 
gross  pathology  is  identical.  The  ears  play  a  more  prominent 
part  in  the  symptomatology,  often  becoming  swollen,  red- 
dened and  drooping.  It  is  possible  to  see  thrombosed  vessels 
in  the  ears  of  white  rabbits,  and  to  watch  the  development 
of  areas  of  dry  necrosis  and  the  separation  of  such  areas  (Figs. 
6  and  7). 

The  following  is  a  typical  record  of  a  rabbit  inoculated 
from  a  guinea-pig.  The  record  of  the  positive  tick  trans- 
mission is  included  on  page  99  in  connection  with  the  pro- 
tocols of  ticks  infected  as  nymphs. 

Record  of  Rabbit  3,  Hayes  strain.  A  three-fourths  grown,  pure  white,. 
male  rabbit,  inoculated  intraperitoneally  with  2  c.c.  of  blood  in  citrate 
saline  solution  from  Guinea  Pig  75,  Hayes  strain. 

December  19,  1918,  inoculated.  Temperatures:  December  20,. 
102.6;  December  21,  102.4;  December  22,  103;  December  24,  103; 
December  26,  105;  December  27,  105.4;  December  28,  106;  Decem- 
ber 29,  105.4,  left  scrotum  red  and  swollen;  December  31,  105. 
January  2,  104,  a  small  ulcer  on  left  scrotum;  January  3,  103.6,  ears- 
swollen,  bluish  red,  marginal  veins  thrombosed;  January  4,  103;  January 
5,  104.6;  January  7,  104,  scrotum  indurated,  ulcer  healed;  January 
8,  102.6;  January  9,  104.6,  dry  necrosis  of  outer  margins  of  ears,  3x2  cm. 
on  left  ear,  about  i  cm.  in  diameter  on  right  ear;  January  25,  separation- 
of  necrotic  portions  of  ears. 

The  histology  of  the  vascular  lesions  in  rabbits  is  identical 
with  that  in  guinea-pigs  except  for  minor  quantitative  differ- 
ences. The  parasite  of  the  disease  occurs  in  equally  large 
numbers  in  the  same  cells  and  situations  as  in  guinea-pigs. 
The  liver  necroses  and  degenerative  changes  in  the  testes 
are  similar;  in  the  latter,  however,  large,  multinucleated  cells 


128  WOLBACH. 

in  the  lumina  of  the  seminiferous  tubules  resulting  from 
atypical  division  of  spermatids  is  a  prominent  feature.  The 
spleen  shows  greater  phagocytosis  of  red  blood  cells  and 
apparently  a  more  rapid  digestion  of  the  phagocytosed  cells 
shown  by  a  more  extensive  pigment  formation  and  the  occur- 
rence of  dark-colored,  fused  corpuscular  masses  in  endothelial 
cells  in  the  splenic  veins  or  sinuses. 

3.  The  disease  in  monkeys  (Figs.  47,  50  and  65).  —  Four 
monkeys  were  inoculated  from  guinea-pigs,  two  were  Rhesus 
macacus,  one  a  South  American  capuchin  and  one  a  Java 
Rhesus.  One  Rhesus  macacus  was  a  female;  the  others  were 
males.  All  proved  equally  susceptible  and  all  succumbed  by 
the  end  of  the  seventh  day.  The  female  macacus  was  killed 
while  moribund  on  the  seventh  day.  The  strains  used  were 
Strain  I.  and  the  Hayes  strain.  No  temperatures  were  taken, 
as  the  objects  of  these  experiments  were  to  observe  the  char- 
acter and  localization  of  the  lesions  and  to  demonstrate  the 
parasite  in  the  lesions.  The  dosages  varied  from  two  to  three 
cubic  centimeters  of  blood  given  intraperitoneally  in  citrate 
saline  solution. 

The  course  of  the  disease  in  these  monkeys  was  rapid. 
The  animals  became  obviously  ill  on  the  fourth  to  fifth  day, 
and  on  the  fifth  or  sixth  day  would  assume  and  maintain 
the  sleeping  posture  until  death.  Swelling  and  redness  of 
the  scrotum  was  observed  in  the  males  on  the  fifth  day. 
In  the  female  no  changes  were  seen  at  the  vulva.  A  slight 
erythema  of  the  chest  and  anus  was  seen  in  the  female  monkey 
before  death. 

The  post-mortem  findings  were  as  follows: 

A  diffuse  dusky  injection  of  the  small  vessels  of  the  skin  and 
subcutaneous  tissues,  but  no  hemorrhages.  Tendon  sheaths 
and  muscle  fasciae  normal.  Inguinal  and  axillary  lymph 
nodes  enlarged  and  reddened.  The  peritoneal  surfaces  were 
normal.  The  pleural  and  pericardial  surfaces  were  normal. 
The  heart  and  lungs  were  normal.  The  spleen  was  enlarged 
in  each  instance  to  about  double  normal  size,  deep  red  in  color, 
and  firm.  The  liver,  pancreas  and  gastro-intestinal  tract  were 
normal.     The  omentum  in  one  instance  was  deeply  injected. 


ROCKY    MOUNTAIN    SPOTTED    FEVER.  1 29 

The  kidneys  were  normal.  The  adrenals  showed  injection 
of  the  medulla,  but  no  hemorrhages. 

The  bladder  was  normal  in  each  instance.  The  retro- 
peritoneal lymph  nodes  were  slightly  enlarged.  In  the  female 
no  lesions  of  the  genitalia  were  found. 

In  the  male  monkeys  the  subcutaneous  tissues  of  the 
scrotum  were  invariably  oedematous  and  deeply  injected  and 
contained  small  hemorrhages. 

The  cremasteric  muscles  were  injected.  The  tunica  vagi- 
nalis in  each  case  was  reddened  and  in  one  instance  studded 
with  petechia;.  The  testes  were  invariably  deeply  injected 
and  swollen.     The  epididymes  were  swollen  and  injected. 

The  organs  of  the  neck,  buccal  and  pharyngeal  mucosae 
showed  no  lesions.  The  brains  and  meninges  showed  no 
lesions. 

This  series,  while  small,  is  significant  in  showing  the  same 
localization  of  lesions  seen  in  guinea-pigs  and  rabbits  and  in 
man. 

Microscopic.  Monkey  4.  —  Heart:  Normal.  Lung: 
There  is  marked  injection  of  the  capillaries  in  the  alveolar 
walls  and  the  capillaries  contain  large  numbers  of  large  mono- 
nuclear cells  with  round  or  horseshoe-shaped  nuclei  and 
numerous  polymorphonuclear  leucocytes.  There  are  rare 
mitotic  cells  in  the  alveolar  wall  capillaries.  The  large  blood 
vessels  and  bronchi  are  normal.  The  alveoli  contain  no 
exudate. 

Spleen:  There  is  marked  injection.  The  Malpighian 
bodies  are  small,  and  many  contain  scattered  polymorpho- 
nuclear leucocytes  and  small  collections  of  large  phagocytic 
mononuclear  cells  which  contain  lymphoid  cells  and  poly- 
morphonuclear leucocytes.  The  reticular  tissue  of  the  pulp 
is  almost  devoid  of  lymphocytes  and  contains  red  blood  cells, 
numerous  polymorphonuclear  leucocytes  and  large  mono- 
nuclear phagocytic  cells.  The  sinuses  and  splenic  veins  con- 
tain many  large  mononuclear  phagocytes,  and  occasional 
masses  of  fused  hyaline-appearing  red  blood  cells,  sometimes 
surrounded  by  one  or  more  phagocytic  cells.  The  arteries 
are  normal. 


130  WOLBACH. 

Liver:  There  is  a  marked  uniform  injection  of  the  sinu- 
soids. There  is  a  marked  uniform  fatty  infiltration  of  the 
liver  cells  in  the  form  of  large  droplets.  An  occasional  single 
liver  cell  is  necrotic  and  invaded  by  polymorphonuclear  leuco- 
cytes. In  the  sinusoids  there  is  a  slight  excess  of  poly- 
morphonuclear leucocytes  and  numerous  large  mononuclear 
phagocytes  (endothelial  cells),  some  of  which  are  attached  to 
the  walls  of  sinusoids.  These  cells  contain  red  blood  cells, 
leucocytes,  and  often  dense,  granular  hyaline  material  sug- 
gesting fused  red  blood  cells.  A  rare  endothelial  is  in  mitosis. 
The  arteries,  veins  and  bile  passages  are  normal. 

Pancreas:  Normal.  Gastro-intestinal  tract:  CEsophagus, 
stomach,  jejunum,  ileum,  colon:  all  normal.  Kidney:  Nor- 
mal. 

Adrenal:  The  veins  and  capillaries  are  greatly  distended 
with  blood.  The  outer  half  to  two-thirds  of  the  fascicular 
zone  shows  a  diffuse  infiltration  of  the  cell  columns  with  poly- 
morphonuclear leucocytes,  and  there  are  small  gaps  in  the 
columns  which  are  filled  with  mononuclear  phagocytic  cells 
(endothelial  cells)  and  polymorphonuclears.  There  are  many 
adrenal  cells  which  show  hyaline  change  and  fragmentation. 
The  capillaries  contain  occasional  endothelial  cells  in  mitosis 
and  free  mononuclear  cells  with  inclusions  of  red  blood  cells 
and  nuclear  fragments.  The  medulla  is  negative  except  for 
the  marked  distention  of  the  blood  vessels. 

Testes  and  adnexa:  A  rare  seminiferous  tubule  shows 
complete  cessation  of  spermatogenesis  with  disappearance  of 
the  spermatids;  such  tubules  being  lined  with  large,  pale, 
elongated  cells,  probably  derived  from  the  sustentacular  cells. 
The  great  majority  of  tubules  are  normal.  The  interstitial 
tissue  in  a  few  places  is  oedematous,  and  occasional  occluded 
vessels  are  found  similar  to  those  in  the  tunica  and  epididymis. 
The  epididymis  and  ductus  deferens  show  no  lesion  of  the 
epithelial  structures.  The  blood  vessels  of  the  tunica  vagi- 
nalis, the  cremasteric  muscles,  the  epididymis  and  pampiniform 
plexus  show  numerous  and  striking  lesions  of  the  intima,  the 
smallest  consisting  of  collections  of  endothelial  cells  attached 
to  the  endothelium,  while  more  extensive  lesions  consist  of 


ROCKY   MOUNTAIN    SPOTTED   FEVER.  I3I 

complete  thrombosis  and  extensive  collections  of  endothelial 
cells  in  the  intima.  There  are  many  mural  thrombi  composed 
of  endothelial  cells,  fibrin  and  polymorphonuclear  leucocytes. 
In  the  testes  and  epididymis  small  veins  and  capillaries  are 
occasionally  completely  filled  with  endothelial  cells,  some  of 
which  are  phagocytic.  The  minute  paired  organisms  are 
present  in  fair  abundance  in  the  endothelial  cells  of  mural 
thrombi  and  in  smaller  collections  attached  to  apparently 
normal  intima  (Fig.  50).  In  tangential  sections  of  arteries 
with  but  slight  lesions  the  organisms  can  be  found  in  the 
smooth  muscle  cells  of  the  media  as  well  as  in  the  endothelium. 

Prostate:  A  rare  blood  vessel  in  the  capsule  shows  lesions 
like  the  above.     The  gland  itself  is  normal. 

Seminal  vesicles  normal.  Urinary  bladder  normal.  Aorta 
normal. 

Lymph  nodes:  Lymph  nodes  from  axilla  and  groin  and 
the  mediastinum  show  a  marked  accumulation  of  large  mono- 
nuclear cells,  some  of  which  are  phagocytic  (endothelial  cells) 
in  the  sinuses.  The  peripheral  lymph  nodes  are  deeply  in- 
jected with  blood  as  well.  All  lymph  nodes  contain  but  few 
polymorphonuclear  leucocytes.  The  secondary  follicles  are 
inactive. 

Skeletal  muscle:  An  occasional  muscle  fiber  is  swollen 
and  convoluted  in  shape,  without  striations,  and  has  assumed 
a  homogeneous,  glassy  appearance  (waxy  degeneration).  A 
rare  small  artery  and  vein  show  lesions  like  those  in  the  testes. 

Skin:  The  skin  from  all  parts  of  the  body  shows  extensive 
lesions  of  the  blood  vessels  with  thromboses  similar  to  those 
of  the  testes  and  epididymis  (Figs.  47  and  65).  The  large 
arteries  and  veins  of  the  subcutaneous  tissue  show  the  most 
marked  lesions,  and  occasionally  the  smooth  muscle  of  the 
media  is  degenerated  and  infiltrated  with  leucocytes  beneath 
a  mural  thrombus.  There  is  a  very  marked  engorgement 
of  all  blood  vessels  of  the  skin.  The  capillaries  of  the  papillae 
occasionally  are  filled  with  endothelial  cells  and  are  rarely 
thrombosed.  The  capillaries  about  the  coil  glands  are  usually 
filled  with  fibrin  and  endothelial  cells.     Complete  thrombosis 


132  WOLBACH. 

of  large  arteries  and  veins  is  rare,  but  is  present  in  the  sub- 
cutaneous tissue.  The  epidermis  and  hair  follicles  and 
sebaceous  glands  are  negative.  The  coil  glands  show  marked 
degenerative  changes,  in  many  instances  the  epithelium  is 
desquamated  and  the  lumen  filled  with  polymorphonuclear 
leucocytes  and  hyaline  cell  debris.  The  minute  paired  or- 
ganism is  present  in  the  endothelial  cells  and  smooth  muscle 
of  blood  vessels  showing  lesions. 

Mucosa  of  the  buccal  cavity:  The  epithelium  and  glands 
are  normal.  In  the  muscle  beneath  the  mucosa  an  occasional 
artery  shows  small  lesions  of  the  intima.  The  organism  is 
present  in  abundance  in  several  such  arteries. 

Brain:  Cortex  cerebri.  Sections  from  five  different  re- 
gions are'  normal.  The  meninges  are  normal.  Cerebellum 
normal.  Choroid  plexus  normal.  Medulla  and  cervical 
cord  normal. 

XVI.       THE    PATHOLOGY    IN   MAN.       SUMMARY, 

The  only  distinctive  gross  features  in  Rocky  Mountain 
spotted  fever  are  those  connected  with  the  distribution  and 
character  of  the  cutaneous  and  subcutaneous  lesions  of  the 
blood  vessels  and  the  lesions  of  the  male  genitalia,  particularly 
the  scrotum  and  the  testes.  The  extensive  hemorrhages 
into  the  scrotal  tissues,  often  with  necrosis  and  similar  lesions 
of  the  testes  and  their  appendages,  are  the  most  character- 
istic gross  findings  in  animals  as  well  as  in  man.  The  spleen 
in  man,  as  in  animals,  is  always  enlarged  to  several  times  the 
normal  size,  and  is  firm  unless  there  has  been  a  secondary 
bacterial  infection. 

The  microscopic  lesions  of  the  disease  are  those  dependent 
upon  focal  lesions  of  the  peripheral  blood  vessels,  and  to  a 
general  increase  of  large  mononuclear  phagocytic  cells  (en- 
dothelial cells)  in  the  capillaries  of  various  organs. 

Heart:  In  Case  I.  there  are  small  collections  of  en- 
dothelial cells  in  the  endocardium  and  a  few  microscopic 
mural  thrombi.  In  Case  V.  there  are  a  few  minute  degenera- 
tive lesions  of  the  myocardium,  and  occasional  intra-  and  peri- 
vascular accumulations  of  endothelial  cells. 


ROCKY   MOUNTAIN    SPOTTED    FEVER.  1 33 

Lung  (Fig.  67) :  The  lungs  from  the  cases  examined  — 
II.,  III.  and  V.  —  show  large  numbers  of  mononuclear  phago- 
cytic cells  (endothelial  cells)  in  the  alveolar  capillaries.  In 
Case  V.  there  is  broncho-pneumonia. 

Spleen  (Fig.  62) :  In  all  four  cases  with  complete  autop- 
sies there  is  extreme  engorgement  with  blood,  almost  com- 
plete loss  of  lymphoid  cells,  and  a  great  accumulation  of  large 
mononuclear  phagocytic  cells  (endothelial  cells)  in  the  splenic 
veins  (sinuses)  and  reticular  tissue.  These  cells  contain  many 
red-blood  corpuscles. 

Liver  (Fig.  61):  There  are  a  few  minute  focal  necroses 
in  all  four  cases,  while  throughout  there  are  many  phagocytic 
mononuclear  cells  (endothelial  cells),  free  in  the  sinusoids  or 
attached  to  the  walls.  These  cells  contain  red-blood  cor- 
puscles and  occasionally  leucocytes.  In  the  liver  of  Case  V. 
a  few  arteries,  veins  and  capillaries  in  the  portal  spaces  show 
small  lesions  of  the  intima  and  a  perivascular  infiltration  of 
endothelial  and  polymorphonuclear  leucocytes.  A  small 
number  of  the  minute  parasites  are  present  in  these  lesions. 

Gastro-intestinal  tract  (examined  only  in  Cases  II.,  III. 
and  V.) :  In  Case  II.  a  single  artery  in  the  wall  of  the  stomach 
was  found  with  a  mural  thrombus.  In  Case  III.  there  are 
several  small  vessels  and  capillaries  with  mural  thrombi. 
The  intestines  are  normal  in  both  of  these  cases.  In  Case  V. 
the  stomach  and  intestines  are  normal. 

Pancreas  (examined  only  in  Cases  II.,  III.  and  IV.):  No 
lesions  are  present. 

Kidneys:  No  acute  lesions  of  the  kidney  tissue  or  blood 
vessels  are  found  in  any  of  the  four  cases.  The  glomerular 
capillaries  contain  a  few  free  endothelial  cells  in  each  case. 

Adrenals  (examined  only  in  Cases  II.,  III.  and  IV.):  No 
lesions  of  importance  are  present.  The  blood  vessels  are 
normal. 

Thyroid  (examined  only  in  Cases  II.  and  IV.;  in  the 
latter  it  is  normal):  In  Case  II.  the  intima  of  arteries  and 
veins  shows  minute  lesions  with  mural  thrombi  like  those  in 
the  vessels  of  the  skin.  These  lesions  contain  the  minute 
parasite  of  the  disease. 


134 


WOLBACH. 


Lymph  nodes  (examined  in  Cases  II.  and  III.)-"  From 
all  regions  —  axillary,  inguinal,  mesenteric  and  bronchial  — 
there  is  a  similar  picture,  namely,  the  accumulation  of  large 
mononuclear  phagocytic  cells  (endothelial  cells)  in  the  sinuses 
and  medullary  areas. 

Aorta  and  large  blood  vessels:  The  aorta  in  Cases  II., 
III.  and  IV.  shows  no  acute  lesions.  The  large  blood  vessels 
in  all  four  cases  of  the  principal  organs  of  the  body  in  no 
instance  contain  lesions. 

Skeletal  muscle:  Muscle  from  Cases  III.,  IV.  and  V. 
shows  occasional  lesions  of  the  blood  vessels  like  those  found 
in  the  skin.  The  muscle  fibers  show  small  patches  of  waxy 
degeneration. 

Central  nervous  system  (examined  in  Case  II.)  is  normal. 

Skin  and  subcutaneous  tissues  (Figs.  44,  51  to  58,  60, 
63,  65,  66  and  70):  The  skin  and  subcutaneous  tissues  taken 
from  all  parts  of  the  body  from  all  five  cases  show  extensive 
lesions  of  the  blood  vessels.  Though  the  lesions  vary  in  degree 
and  number,  they  represent  the  same  process,  and  for  this 
reason  but  one  description  of  their  character  is  given,  based 
on  a  careful  study  of  many  blocks  from  each  case.  The 
number  of  affected  vessels  in  the  skin  corresponds  roughly 
with  the  extent  and  age  of  the  rash;  for  instance,  there  is 
greater  involvement  of  the  vessels  of  the  skin  of  the  legs  than 
of  the  skin  of  the  abdomen,  which  agrees  with  the  evolution 
of  the  eruption.  Similarly,  in  the  male  the  lesions  of  the 
vessels  of  the  scrotum  are  very  numerous  and  marked. 

The  most  striking  lesions  are  found  in  large-sized  arteries 
and  veins  of  the  lower  layer  of  the  corium,  and  in  the  sub- 
cutaneous fat,  where  completely  thrombosed  vessels  are  com- 
mon. The  earliest  lesion  in  these  vessels  is  a  collection  of 
large  mononuclear  phagocytic  cells  (endothelial  cells)  over  an 
area  of  swollen  and  degenerated  endothelium  of  the  intima 
(Figs.  60,  63  and  66).  In  arteries  there  is  fragmentation  of 
the  internal  elastic  lamina  and  collections  of  polymorpho- 
nuclear leucocytes  beneath  it  and  in  the  media.  In  these  early 
lesions  the  minute  paired  parasite  is  found  in  large  numbers, 
in  endothelial  cells,  and  in  smooth  muscle  cells  of  the  media. 


ROCKY   MOUNTAIN    SPOTTED    FEVER.  1 35 

Many  of  the  endothelial  cells  and  smooth  muscle  cells  con- 
taining the  parasites  show  hyaline  change  and  a  preference 
for  the  basic  stains.     More  extensive,  and  presumably  later, 
lesions  affect  the  whole  circumference  of  the  vessel,  so  that 
there  may  be  a  concentric  thickening  of  the  intima  due  to 
the  accumulation  of  endothelial  cells  upon  and  in  the  intima 
(Figs.  51  and  54).     Fibrin  deposits  are  found  about  degener- 
ated endothelial  cells  and  in  the  media,  and  finally  complete 
thrombosis  results.     In  longitudinal  sections  of  vessels    (Fig. 
51)  it  is  possible  to  see  numerous  foci  of  fibrin  deposit  along 
the  course  of  the  thickened  intima.     The  extension  of  fibrin 
thrombi  beyond  the  seat  of  the  initial  lesion  accounts  for  the 
finding  of  cross-sections  of  vessels  filled  with  fibrin  thrombi 
without  marked  lesions  of  the  wall.     In  late  lesions  the  whole 
vessels  wall  becomes  infiltrated  with  endothelial  and  poly- 
morphonuclear leucocytes;   and  surrounding  the  vessel  a  zone 
of    large    mononuclear    phagocytic    cells    (endothelial    cells) 
forms.     Early  stages  of  repair  were  seen  in  Case  I.  in  vessels 
of  the  skin  of  the  legs,  in  beginning  canalization  of  thrombi. 
The  minute  paired  parasites  are  most  numerous  in  the  early 
and  moderately  advanced  lesions.     They  vary  in  size;   larger, 
lanceolate  forms,  in  pairs,  which   together  measure  slightly 
less  than  one  micron  in  length,  are  found  in  endothelial  cells 
and  in  smooth  muscle  cells  (Figs.  44,  63,  66).     Much  more 
minute  forms  occur  in  enormous  numbers  in  smooth  muscle 
cells,  and  these  forms  are  comparable  in  size  to  the  intra- 
nuclear forms  found  in  ticks. 

Lesions  of  the  papillary  capillaries  and  subpapillary  plexus 
of  the  skin  are  in  general  similar  to  those  of  the  larger  vessels, 
though  modified  by  the  difference  in  thickness  of  the  vessel 
walls.  Briefly,  these  vessels  become  filled  with  proliferated 
endothelial  cells  (Fig.  70),  some  of  which  become  necrotic. 
Perivascular  collections  of  endothelial  cells  occur  also  with 
necrosis,  and  then  accumulations  of  polymorphonuclear  leuco- 
cytes (Figs.  57  and  58).  Thrombi  of  fibrin  are  found. 
The  plexuses  of  capillaries  around  the  coil  glands  are  particu- 
larly liable  to  these  lesions.  Infiltration  of  nerves  with  poly- 
morphonuclear leucocytes  and  mononuclear  amoeboid  cells 
(endothelial    cells)  was  found  in  Cases  I.  and  II. 


136  WOLBACH. 

The  epidermis  may  show  changes  dependent  upon  the  in- 
farctions of  minute  areas  of  the  corium.  Microscopical  losses 
of  epidermis  occur. 

The  lesions  of  the  skin  of  the  ears  and  scrotum  of  guinea- 
pigs  and  rabbits,  and  of  the  skin  of  the  scrotum  in  monkeys, 
are  identical  in  character  with  those  of  the  human  cases,  — 
initial  endothelial  cell  proliferation,  followed  by  thrombosis 
and  perivascular  proliferation. 

Testes  and  adnexa:  In  all  four  male  cases  very  extensive 
lesions,  similar  in  all  respects  to  those  of  the  skin  and  sub- 
cutaneous vessels,  are  found  in  the  arteries,  veins  and  capil- 
laries of  the  testes,  epididymis  and  pampiniform  plexus.  The 
parasites  are  as  numerous  in  these  locations  as  in  the  skin. 

The  lesions  of  Rocky  Mountain  spotted  fever  in  man  and 
in  experimental  animals  are  practically  restricted  to  the  pe- 
ripheral blood  vessels,  including  those  of  the  external  genitalia. 
The  vascular  lesion  is  in  the  beginning  a  proliferative  lesion 
on  the  part  of  the  vascular  endothelium.  Varying  degrees 
of  intensity  in  the  reaction  are  encountered,  so  that  poly- 
morphonuclear leucocytes  may  or  may  not  play  a  part  in 
the  lesions  before  the  occurrence  of  thrombosis.  Following 
thrombosis,  polymorphonuclear  leucocytes  are  of  necessity 
present.  A  direct  injury  to  cells  by  the  parasite  is  shown 
by  the  degenerative  changes  found  in  the  endothelial  cells 
and  in  the  smooth  muscle  cells  of  the  media,  which  are  also 
invaded  by  the  parasite.  The  general  reaction  to  the  disease, 
and  possibly  to  the  toxin  of  the  parasite,  is  shown  by  the 
finding  of  endothelial  cell  accumulations  in  the  blood  vessels 
of  the  lung,  liver,  spleen,  and  in  the  lymph  nodes. 

One  feature  of  Rocky  Mountain  spotted  fever  which  cannot 
be  too  strongly  emphasized  is  that  it  may  be  exactly  duplicated 
in  experimental  animals.  This  duplication  of  the  clinical  and 
pathological  picture  takes  place  no  matter  how  the  virus  is 
introduced,  whether  by  intraperitoneal  or  subcutaneous  in- 
oculation, or  through  the  medium  of  a  tick.  When  trans- 
mitted by  a  tick,  the  incubation  period  is  about  the  same  as 
that  in  man.     In  non-fatal  cases,  the  duration  of  the  disease 


ROCKY    MOUNTAIN    SPOTTED   FEVER.  1 37 

is  about  the  same.  The  character  of  the  temperature  curve 
is  almost  identical,  but  most  striking  of  all  is  the  exact  dupli- 
cation of  the  pathology,  both  in  regard  to  the  tissues  affected 
and  in  the  distribution  of  the  lesions.  In  all  animals,  as  well 
as  in  man.  Rocky  Mountain  spotted  fever  is  a  disease  of  the 
peripheral  blood  vessels,  an  acute  specific  infectious  endan- 
giitis. 


XVII.      CASE    REPORTS. 

Case  I.  —  A  well-developed,  vigorous  woman,  age  26  years,  a  new 
arrival  and  resident  in  Saw  Tooth  Canyon,  in  the  Bitter  Root  Valley, 
near  Hamilton,  became  ill  on  April  27.  On  April  23  a  partially  engorged 
tick  was  removed  from  the  back  of  her  neck.  The  first  symptoms  noted 
were  pains  in  the  arms  and  legs  and  flushing  of  the  face.  On  May  i  she 
noticed  a  rash  on  her  legs  and  she  came  to  Hamilton  for  medical  care. 
When  examined  on  the  evening  of  May  i  she  had  a  short,  moist  cough; 
her  face  was  flushed  and  there  was  a  mottled  erythema  over  the  forehead 
and  neck  and  a  macular  eruption,  disappearing  upon  pressure,  thickly 
distributed  over  the  whole  body,  but  most  prominent  over  the  arms, 
shoulders,  buttocks  and  legs.  The  temperature  was  105°  F.,  pulse  96, 
respirations  24.  She  was  extremely  .restless,  slept  for  a  period  of  fifteen 
minutes  only  during  the  night,  and  vomited  several  times.  On  May  2, 
by  daylight,  a  slight  yellowish  cast  of  the  skin  was  apparent  and  the  rash 
was  more  apparent.  The  lesions  averaged  about  one  to  each  square 
centimeter  of  surface,  were  i  to  3  mm.  in  diameter,  just  perceptibly  ele- 
vated and  disappeared  upon  pressure.  There  was  a  marked  erythematous 
mottling  of  the  forehead,  the  face  was  flushed,  the  conjunctivae  moderately 
injected  and  the  tongue  coated.  The  buccal  mucosa,  the  fauces,  tonsils 
and  palate  were  negative. 

The  treatment  consisted  of  enemas,  calomel,  and  "  aspirin  "  in  large 
doses.  To  this  last  rhay  be  attributed  the  low  temperature  from  this 
date.  The  diet  was  restricted  to  liquids,  largely  buttermilk  and  lemon- 
ade. Tepid  sponge  baths  were  given.  The  patient  continued  to  be  rest- 
less and  did  not  sleep.  On  May  3,  the  rash  seemed  less  pronounced.  Her 
mental  condition  was  good  though  she  complained  of  a  severe  headache. 
At  noon,  125  cc.  of  blood  was  transferred  by  the  indirect  method  in  a 
paraffined  tube  from  an  immune  donor.  White  blood  count  at  3.00  p.m.,. 
7,300.     During  the  night  she  became  delirious  and  got  out  of  bed. 

On  May  4  her  condition  was  worse.  She  had  a  hard,  dry  cough.  The 
skin  of  the  face,  neck  and  thighs  was  cyanotic,  and  a  deep  mottling  of  dull 
red  appeared  on  the  thighs.  She  became  extremely  sensitive  to  the  touch; 
the  slightest  pressure  over  the  tibia  for  instance  caused  severe  pain.  The 
yellowish  cast  to  the  skin  was  now  pronounced.  The  tongue  was  heavily 
coated  along  the  middle  third;  the  edges  were  clear.  The  throat,  palate, 
tonsils  and  buccal  mucosa  appeared  to  be  normal.     During  the  afternooa 


138 


WOLBACH. 


she  became  slightly  delirious  and  again  passed  a  sleepless  night.     White 
•blood  cell  count,  7,300.     Red  blood  cell  count,  5,008,000. 

On  May  5  the  cyanosis  and  icterus  were  more  pronounced.  There 
was  a  marked  dilatation  of  the  veins  on  the  outer  surfaces  of  the  thighs, 
marked  cyanosis  of  the  legs,  and  a  few  petechise  on  the  thighs  and  buttocks. 
The  cutaneous  hypercesthesia  became  so  marked  that  the  pressure  of  the 
bedclothes  became  unbearable.  There  was  also  severe  deep  pain  in  the 
legs.  Towards  evening  the  increase  in  the  number  and  size  of  the  petechias 
was  pronounced  and  the  thighs  assumed  a  marbled  appearance  due  to  the 
prominence  of  the  engorged  veins  of  the  skin. 


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Charts  of  temperature,  pulse  and  respiration  of  Case  I.     Woman,  age  26. 
Death  on  ninth  day  of  disease. 


On  May  6  in  the  early  morning  she  was  mildly  delirious  and  almost 
moribund.  Her  arms  and  legs  became  dull  red  and  cold.  Death  occurred 
at  3.00  P.M.  Rigor  mortis  set  in  almost  immediately.  After  death  there 
was  a  marked  blanching  of  the  skin  of  the  trunk  and  legs.  The  distended 
veins  of  the  thighs  had  disappeared  but  dull  red  areas  0.3  to  0.7  cm.  in 
diameter  remained.  The  face  remained  cyanosed  and  bloated  in  appear- 
ance. 


ROCKY    MOUNTAIN'    SPOTTED   FEVER.  I39 

No  post-mortem  was  permitted.  Pieces  of  skin  were  removed  from 
the  arms,  buttocks,  thighs,  legs  and  ankles.  Incision  of  the  skin  of  the 
thigh  through  the  persistent  red  areas  showed  these  to  be  due  to  extrava- 
sated  blood  in  the  corium  and  subcutaneous  fat. 

The  urine  was  examined  but  once  owing  to  menstruation,  which  was  in 
progress  upon  admission.  On  May  5  the  specific  gravity  was  1,021, 
color  pale,  perfectly  transparent.  There  was  the  slightest  possible  trace 
of  albumin,  no  sugar.  No  microscopic  examination  was  made.  The 
differential  blood  counts  are  given  on  page  32. 

Throughout  the  illness,  examination  of  the  chest  was  negative.  The 
behavior  of  the  heart  is  shown  in  the  chart,  the  pulse  became  progressively 
more  feeble  with  increasing  rapidity. 

The  heavy  "  aspirin  "  medication,  275  grains  in  all,  was  responsible 
for  the  relatively  low  temperature  maintained  after  the  first  day  in  the 
liospital. 

Two  guinea-pigs  inoculated  each  with  five  cubic  centimeters 
of  blood  in  citrate  sahne,  taken  on  May  3,  developed  typical 
lesions  and  temperatures  of  spotted  fever.  From  these 
guinea-pigs  the  strain  was  maintained  for  three  generations 
while  infecting  ticks  and  then  voluntarily  abandoned. 

Spotted  fever  Case  I.  Microscopic  description.  Eosin, 
methylene-blue  and  Giemsa  stains  (Figs.  53,  54  and  57). 
Skin  from  buttocks:  There  is  marked  injection  of  all 
blood  vessels.  There  are  striking  acute  lesions  of  blood 
vessels  of  all  sizes.  Arteries  and  veins  of  large  size  in  the 
deep  layer  of  the  corium  and  subcutaneous  fat  contain  lesions 
of  the  intima  and  often  mural  and  occluding  thrombi  of 
fibrin  and  cells,  and  the  walls  are  often  infiltrated  with  leuco- 
cytes. Small  vessels  in  the  fat  tissue  and  in  the  corium  are 
thrombosed  and  surrounded  by  collections  of  cells.  The 
papillary  capillaries  of  the  skin  and  capillaries  surrounding 
coil  glands  are  filled  with  large  cells  and  surrounded  by  col- 
lections of  cells.  The  vessels  of  the  subpapillary  plexus  are 
similarly  affected.  The  epidermis  shows  no  apparent  change. 
The  coil  glands  often  show  marked  vacuolization  of  the  cells, 
and  many  contain  only  desquamated  cells  with  pycnotic 
nuclei.  Hair  follicles  and  sebaceous  glands  show  no  apparent 
change. 


140  WOLBACH. 

The  smallest  lesions  of  arteries  and  veins  consist  of  small 
masses  of  fibrin  attached  to  the  intima  and  usually  completely 
surrounded  by  endothelial  cells.  Larger  lesions  consist  of 
extensive  masses  of  coarsely  reticulated  hyaline  fibrin,  some 
strands  of  which  may  extend  into  the  media,  enclosing  poly- 
morphonuclear leucoc^'tes  and  large  mononuclear  phagocytic 
cells  (endothelial  cells)  and  granular  nuclear  remains.  The 
surface  of  the  fibrin  is  covered  with  large,  flattened  endothehal 
cells,  continuous  vrith  the  vascular  endothelium  and  poly- 
morphonuclear leucoc\i:es.  The  media  is  usually  heavily  in- 
filtrated with  pohmorphonuclear  leucoc\-tes  and  mononuclear 
phagocytic  cells  (endothelial  cells).  The  adventitia  and  sur- 
rounding connective  tissue  often  contains  large  numbers  of 
large  mononuclear  cells,  some  of  them  phagocytic,  lymphoid 
and  plasma  cells  and  pohtnorphonuclear  leucoc\tes.  Smaller 
arteries  and  veins  are  completely  filled  with  large  branching 
cells  attached  to  the  vessel  wall,  phagocytic  cells  and  poly- 
morphonuclear leucocytes  in  a  fibrin  meshwork  (early  or- 
ganization). The  capillaries  of  the  papillae  and  coil  glands 
are  sometimes  occluded  by  fibrin  and  large  mononuclear 
phagocytic  cells  (endothelial  cells^  and  polymorphonuclear 
leucocytes;  they  are  often  surrounded  by  zones  of  similar 
cells.  Other  capillaries  are  patent,  contain  numerous  large 
mononuclear  phagocytic  cells  enclosing  red  blood  corpuscles 
and  other  cells  and  are  surrounded  by  narrow  zones  of  lymph- 
oid and  plasma  cells,  mononuclear  phagocytic  cells  and  an 
occasional  eosinphile. 

The  nerves  for  the  most  part  show  no  lesions:  a  few,  how- 
ever, contain  large  mononuclear  cells,  mast  cells  and  a  rare 
polymorphonuclear  leucocyte.  One  ner^e  trunk  of  large  size 
contains  a  capillan.-  occluded  and  surrounded  by  endothelial 
cells  and  polymorphonuclear  leucocytes.  In  the  fat  lobules 
below  the  corium  there  are  a  few  small  areas  of  hemorrhage, 
occasionally  in  relation  to  a  vessel  with  marked  lesions. 
In  a  few  vessels  shoTi-ing  lesions  there  are  numbers  of  minute 
paired  organisms,  sometimes  round,  sometimes  lanceolate  in 
shape,  and  usually  surrounded  by  a  narrow  clear  zone  or  halo. 
These  organisms   occur  in   swollen   endothelium   iti  situ,   irt 


ROCKY    MOUXTAIX    SPOTTED    FEVER.  I41 

rounded  endothelial  cells,  in  fibrin  and  rarely  packed  in  a 
smooth  muscle  fiber.  The  length  of  the  pairs  measures 
slightly  less  than  one  micron ;  the  breadth  is  estimated  at  about 
one  fourth  of  a  micron. 

Skin  from  thigh:  The  lesions  are  identical  with  those  of 
the  skin  from  the  buttock.  There  are  many  vessels  of  large 
caliber  in  these  sections,  and  several  arteries  and  veins  are 
found  with  beginning  organization  and  canalization  of  the 
fibrin  thrombi,  and  such  vessels  usually  show  no  infiltration 
of  the  media.  The  minute  parasites  cannot  be  found  in  the 
vessels  with  these  older  lesions.  A  fair-sized  vein  in  the 
subcutaneous  fat,  cut  longitudinally,  shows  a  valve  covered 
on  the  proximal  side  with  a  thrombus  composed  of  fibrin, 
large  numbers  of  mononuclear  phagocytic  cells  (endothelial 
cells)  and  polymorphonuclear  leucocytes.  In  the  endothelium 
of  the  vein  adjacent  to  the  thrombus  are  several  pairs  of  the 
minute  organisms. 

Skin  from  arms:  The  lesions  are  similar  to  those  described, 
though  less  numerous. 

Skin  from  lower  leg:  The  vascular  lesions  of  the  sub- 
cutaneous tissue  of  the  leg  are  more  numerous  than  from 
any  of  the  other  locations,  though  identical  in  nature.  The 
minute  parasites  are  found  in  the  lesions  in  endothelium  and 
smooth  muscle.  The  subcutaneous  fat  shows  more  hemor- 
rhages, and  the  connective  tissus  septa  are  oedematous.  Many 
fat  cells  are  shrunken  and  filled  with  faintly  staining  granular 
material,  mapy  are  surrounded  by  large  crescentic  cells,  occa- 
sionally multinucleated  with  foam-like  cytoplasm.  There  are 
a  few  oval  and  round  giant  cells  occupying  spaces  and  filled 
with  fat.  Between  fat  cells  there  are  occasional  large  mono- 
nuclear cells  (endothelial  cells)  which  have  taken  up  red  blood 
corpuscles  and  other  cells,  probably  lymphoid  cells. 

Case  II.  Hayes.  —  This  case  was  that  of  a  stalwart,  old  white  man, 
75  or  76  years  old,  who  lived  on  O'Brien  Creek,  a  tributary  of  the  Bitter 
Root  River.  He  was  employed  in  placing  poisoned  baits  for  ground  squir- 
rels, and  was  notoriously  careless  in  regard  to  ticks,  and  took  but  little 
trouble  to  remove  them  from  his  person.  Several  days  before  the  onset 
of  his  illness  he  complained  of  a  particularly  irritating  bite  over  his  right 


142 


WOLBACH. 


scapula.  The  onset,  as  far  as  could  be  determined,  began  the  evening  of 
May  2  with  severe  pains  in  his  legs  and  back  and  burning  sensations  of 
his  feet  and  ankles,  which  he  said  felt  as  if  they  were  parboiled.  He  did 
not  report  for  work  on  May  3.  On  May  4  he  claimed  to  have  had  dysen- 
tery. On  May  5  he  had  nausea  and  vomiting  but  remained  up.  On 
May  6  he  was  found  on  the  ground,  delirious,  too  weak  to  walk  to_,the 
well  for  which  he  had  started.  He  was  taken  to  St.  Patrick's  Hospital 
on  the  evening  of  May  6,  where  several  ticks  were  detached  from  his  body. 


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Charts  of  temperature,  pulse  and  respiration  of  Case  II. 
Death  on  sixth  day  of  disease. 


Male,  age  75. 


A  rash  was  first  noticed  on  May  7  in  the  form  of  faint  red,  non-elevated 
areas  .3  to  .5  cm.  in  diameter,  thickly  scattered  over  his  body  but  most 
marked  on  his  arms,  shoulders,  thighs  and  legs.  These  areas  disappeared 
upon  pressure.  The  face  was  flushed  in  appearance  in  spite  of  a  heavy 
coat  of  tan.  The  conjunctivae  were  injected.  He  remained  in  a  semi- 
conscious state,  with  lax  muscles,  insensible  to  ordinary  stimuli,  but  capa- 
ble of  being  roused  sufficiently  to  answer  questions. 

On  May  8  the  rash  was  more  pronounced.  There  was  a  yellowish  cast 
to  the  skin  and  a  slight  general  cyanosis  of  the  skin  of  the  legs  and  thighs. 


ROCKY   MOUNTAIN    SPOTTED   FEVER.  1 43 

He  was  completely  unconscious  and  died  quietly  at  11.30  a.m.  after  several 
periods  of  stertorous  respiration. 

The  blood  counts  fifteen  minutes  before  death  were:  Red  blood  cor- 
puscles, 6,072,000;   White  blood  corpuscles,  2,100. 

A  differential  white  count  made  on  May  7  is  recorded  on  page  32. 

Two  guinea-pigs  were  inoculated  on  May  7,  each  intra- 
peritoneally,  with  five  cubic  centimeters  of  blood  in  citrate 
saline  solution.  Both  developed  typical  lesions  and  tem- 
peratures of  spotted  fever.  Ticks  were  infected  by  feeding 
upon  one  of  these  guinea-pigs  and  from  these  ticks  the  strain 
was  again  established  in  Boston.     (See  Chart  4,  page  59.) 

Autopsy.     Spotted  fever,  Case  II.     One  and  a  half  hours 
post-mortem.      Missoula,  Mont.,  May  8,  1917,  at  i.oo  p.m. 
(by  daylight).  —  Body:     Is  that  of  a  tall,  well-developed  and 
fairly  well-nourished  white  man,  180  centimeters  long.     Body 
heat  present.     No   rigor.     Very  slight  post-mortem  lividity 
in  dependent  parts.     There  is  a  marked  arcus  senilis  on  each 
cornea.     On  the  left  cornea  there  is  a  linear  horizontal  opacity 
three  millimeters  long.     The  pupil  is  eccentrically  situated 
towards  the  inner  margin;  measures  .2  millimeter.    The  iris  is 
irregularly  pigmented  brownish.     The  right  pupil  measures  .4 
millimeter,  is  symmetrical.     On  the  scalp  over  the  right  fron- 
tal bone  posteriorly  is  a  series  of  shallow  linear  abrasions  of  the 
skin,  covering  an  area  two  by  three  centimeters.     On  the  left 
side  of  the  neck  behind  the  sterno-cleido-mastoid  muscle  is 
an  elevated  circular  lesion  .4  centimeter  in  diameter,  with  a 
central  excoriated  and  crusted  brownish  area  .2  centimeter 
in  diameter.     The  adjacent  skin  is  not  discolored.     In  the 
right  axilla  is  a  similar  lesion.     Over  the  pubis  is  a  similar 
somewhat  larger  lesion,  with  a  central  excoriation  .4  milli- 
meter in  diameter.      (These  lesions  are  said   to  be  typical  of 
the  bites  of  Dermacentor.)     Above  and  to  the  right  of  the 
pubic  hair  is  a  shallow  ulcer  (caused  by  the  excision  of  the 
skin  to  which  a  tick  was  fastened).     On  the  buttocks,  arms, 
thighs  and  legs  are  a  few  dull  red  areas  and  innumerable 
punctate  red  spots.     There  are  similar  lesions  on  the  sides 
and    back   of   the   abdomen.     The    pendent    portion    of   the 
scrotum  is  discolored  deep  red.     There  is  no  oedema. 


144  WOLBACH. 

Incision  of  the  skin  in  various  places  reveals  an  occasional 
reddish  area  in  the  subcutaneous  fat  just  beneath  the  corium. 
Incision  down  to  the  tendons  of  the  foot  on  the  front  of  the 
ankle  shows  a  marked  capillary  injection  of  the  walls  of  the 
tendon  sheaths.  The  subcutaneous  tissues  of  the  scrotum  are 
infiltrated  with  sanguineous  fluid.  The  ears  and  nasal  sinuses 
are  normal.  The  mouth  is  clean.  Five  teeth  only  are  present, 
the  left  lower  lateral  incisor  and  canine,  the  right  lower  lateral 
incisor,  canine  and  first  bicuspid.  There  are  no  teeth  on  the 
upper  jaw. 

Peritoneal  cavity:  The  subcutaneous  fat  of  the  abdomen  is 
pale  yellow,  one  centimeter  deep,  and  not  discolored.  The 
miuscles  are  firm,  deep  red  in  color.  The  peritoneal  surfaces 
are  everywhere  smooth,,  glistening,  moist,  no  free  liquid;  no 
adhesions.  The  appendix  is  six  centimeters  long,  hangs  de- 
pendent, has  a  mesentery  to  its  tip.  The  mesenteric  lymph 
nodes  and  retroperitoneal  lymph  nodes  along  the  vertebrae 
are  small  and  pale  in  color.  The  stomach  and  intestines  are 
contracted.  The  colon  contains  a  moderate  amount  of  gas. 
The  diaphragm  reaches  to  the  fifth  rib  on  the  right,  the  fifth 
interspace  on  the  left. 

Pleural  cavities:  The  lungs  are  voluminous,  pale,  and  at 
the  instant  of  opening  bulge  forth  from  the  chest.  They 
collapse  upon  handling.  The  left  cavity  is  free  from  adhesions 
and  liquid.  The  right  lung  is  adherent  to  the  chest  wall  at 
the  apex  by  loose,  tough  fibrous  tissue.     No  free  liquid. 

Pericardial  cavity:  Contains  about  forty  cubic  centimeters 
of  clear  pale-yellow  liquid.     Normal. 

Heart:  Contracted  in  systole.  On  removal,  dark-red  liquid 
blood  escapes  from  the  great  vessels  in  great  quantity.  This 
blood  clotted  in  a  few  minutes  in  the  chest  cavities.  The 
heart  is  normal  in  size.  The  myocardium  is  deep  brownish 
red,  firm  in  consistency  and  on  section  is  perfectly  uniform- 
The  valves  and  endocardium  are  normal.  Just  above  the 
aortic  valve,  in  the  aorta,  are  a  few  small  pale  elevations  of 
the  intima  two  or  three  millimeters  in  diameter.  None  are 
calcified. 


ROCKY   MOUNTAIN    SPOTTED   FEVER.  1 45 

Lungs:  Both  lungs  are  \'oluminous.  The  alveoli  along 
the  borders  remain  distended  with  air  after  collapse  of  the 
lungs  as  a  whole.  The  left  lung  is  pale  purplish-gray,  with 
moderate  anthracosis.  The  posterior  border  is  dull  red.  The 
consistency  of  the  whole  lung  is  soft,  crepitant.  On  section 
the  cut  surfaces  are  pale  grayish-pink  and  dry,  posterior 
border  red ,  due  to  post-mortem  settling. 

Right  lung:  The  apex  is  distorted  by  irregular  bands  of 
cicatricial  tissue.  Embedded  in  the  upper  part  of  the  upper 
lobe,  beneath  the  apex,  are  two  hard  masses,  one  1.5  by  one 
centimeter,  the  other  two  by  one  centimeter.  These  on  sec- 
tion have  hard,  calcified  walls  one  to  two  millimeters  thick, 
and  are  filled  with  gritty,  clay-colored  plastic  material.  The 
adjacent  lung  tissue  is  soft,  crepitant,  but  is  deeply  pigmented 
grayish  to  black.  The  remainder  of  the  right  lung  is  similar 
to  the  left  lung.  The  bronchi  of  both  lungs  are  slightly  in- 
jected, pink,  and  contain  a  small  amount  of  tenacious  froth. 
The  bronchial  lymph  nodes  are  small,  soft,  black,  uniform  on 
section. 

Spleen:  The  spleen  is  greatly  enlarged,  measures  16  by 
lb  by  7  centimeters.  The  capsule  is  smooth,  tense,  the 
borders  are  rounded.  The  color  is  dark  red,  almost  black. 
The  consistency  is  resilient  and  firm.  On  section  the  cut 
surfaces  are  smooth,  very  dark  red,  almost  black.  The 
trabeculae  and  Malpighian  corpuscles  are  not  visible.  On 
scraping  the  cut  surface  dark-red  blood  is  yielded. 

Liver:  Normal  in  size.  The  color  is  reddish  brown.  On 
section  the  lobular  markings  are  visible  with  difficulty.  The 
consistency  is  normal.  The  gall  bladder  and  ducts  are  normal 
and  contain  transparent  yellowish-green  bile. 

Gastro-intestinal  tract:  The  stomach  and  intestines  are 
contracted  and  almost  empty  of  contents.  On  the  posterior 
wall  of  the  stomach  is  a  red  area,  .4  centimeter  in  diameter 
in  the  mucosa,  otherwise  no  lesions  found  in  oesophagus 
stomach  and  intestines.  The  colon  contains  a  few  solid  parti- 
cles of  feces  and  a  moderate  amount  of  gas.  The  mucosa  is 
normal. 

Pancreas:    Normal  in  size,  color  and  consisterc). 


146  WOLBACH. 

Kidneys:  Normal  in  size.  The  capsules  strip  easily  from 
smooth  surfaces.  The  cortices  average  .6  centimeter  in 
width  and  are  pale  in  color.  The  pyramids  are  moderately 
injected.  Pelves  and  ureters  normal.  Adrenals  normal  in 
size,  color  and  consistency.  Bladder  normal.  Prostate 
slightly  enlarged  symmetrically;  measures  3  by  3.5  centi- 
meters; firm.  On  section,  each  lateral  lobe  contains  several 
small,  dense  nodules  .2  to  .3  centimeter  in  diameter. 

Testicles  and  scrotum:  The  subcutaneous  tissues  of  the 
scrotum  are  deep  red  and  wet.  The  parietal  tunica  vaginalis 
is  injected.  The  surfaces  of  the  epididymis  are  deeply  in- 
jected, and  the  areolar  tissues  are  deep  red  and  wet.  On 
section  the  testicles  appear  normal  except  for  small  injected 
areas  beneath  the  tunica.  The  first  portions  of  the  spermatic 
cord  are  deeply  injected. 

Aorta:  There  are  numerous  small,  pale-yellowish,  smooth, 
slightly  elevated  areas  scattered  throughout  the  intima;  none 
are  calcified  or  of  soft  consistency.  The  caliber  of  the  aorta 
is  normal. 

Organs  of  the  neck,  and  mouth  cavity:  The  trachea  is 
moderately  injected.  Larynx  and  pharyngeal  mucosa  are 
normal.  The  tonsils  are  small;  normal.  The  posterior  part 
of  the  tongue  is  covered  with  a  grayish  layer;  otherwise  nor- 
mal.    Thyroid  gland  normal  in  size,  color  and  consistency. 

Peripheral  lymph  nodes:  The  lymph  nodes  of  the  axillae 
are  slightly  injected,  not  enlarged.  Those  of  the  inguinal 
region  are  pale,  wet  and  slightly  enlarged.  Those  along  the 
carotid  vessels  are  slightly  injected. 

Bone  marrow:  From  the  femur  is  entirely  fatty,  yellow 
in  color. 

Head:  The  hair  is  short,  white,  sparse.  The  subcutaneous 
tissue  of  the  scalp  is  finely  injected  and  presents  a  dusky  red 
tracery  of  minute  vessels.  The  calvarium  is  normal.  Dura 
and  sinuses  normal.     The  Pacchionian  bodies  are  small. 

Brain:  The  arachnoid  encloses  an  excess  of  clear,  colorless 
liquid.  The  vessels  of  the  pia  arachnoid  are  deeply  injected, 
over  the  whole  brain,  most  markedly  over  the  vertex,  and 
over  the  inferior  surface  of  the  pons  and  medulla,  and  over  the 


ROCKY   MOUNTAIN    SPOTTED    FEVER.  I47 

superior  worm  of  the  cerebellum.  The  sulci  of  the  frontal 
lobes  are  wide  and  filled  with  clear  fluid.  There  is  no  flatten- 
ing of  convolutions  and  the  consistency  of  the  brain  is  normal. 
Nothing  abnormal  found  on  section  of  the  hemispheres,  basal 
ganglia,  pons,  medulla  and  cerebellum.  The  ventricles  con- 
tain clear  fluid,  are  not  dilated.  The  choroid  plexuses  are 
normal.  Vessels  at  base  of  brain,  normal.  Sinuses  at  base 
of  skull  are  normal. 

Anatomical  diagnoses.  —  Acute  splenitis.  Exanthem  of 
skin,  with  rare  subcutaneous  extravasations  of  blood.  Healed 
pulmonary  tuberculosis.     Acute  epididymitis  and  periorchitis. 

Spotted  fever  Case  II.  Microscopic  description.  Eosin- 
methylene-blue  and  Giemsa  stains  (Figs.  55,  60,  61,  62, 
66,  67  and  68).  —  Heart:  A  section  through  left  ventricle 
wall  and  base  of  anterior  group  of  papillary  muscles.  There 
are  a  few  areas  of  dense  fibrous  tissue  in  the  ventricle  wall, 
enclosing  fibers  in  various  stages  of  atrophy.  In  a  band  of 
conduction  fibers  beneath  the  endocardium  is  a  small  collection 
of  polymorphonuclear  leucocytes,  with  a  few  large  mononu- 
clear cells  (endothelial  cells)  and  mast  cells,  all  lying  between 
the  muscle  fibers  which  appear  to  be  uninjured.  Attached 
to  the  endocardium,  between  two  muscle  columns,  is  a  small 
thrombus,  composed  of  finely  meshed  fibrin  enclosing  many 
large  mononuclear  cells,  some  of  which  are  phagocytic,  poly- 
morphonuclear leucocytes  and  lymphoid  cells.  The  intima 
adjacent  to  and  beneath  this  thrombus  is  infiltrated  with 
large  mononuclear  cells  (endothelial  cells),  lymphoid  and 
plasma  cells,  and  a  rare  polymorphonuclear  leucocyte.  The 
epicardium  and  the  endocardium  in  a  few  places  where  there 
is  no  thrombus,  is  similarly  infiltrated.  There  is  a  marked 
increase  in  the  perinuclear  pigment  of  the  muscle  fibers. 
The  arteries  of  the  myocardium  show  moderate  arteriosclero- 
sis, but  no  acute  lesions. 

Lung  (Fig.  67):  There  is  moderate  injection  with  blood; 
no  exudate.  The  bronchi  are  normal.  The  alveolar  walls 
are  everywhere  slightly  thicker  than  normal,  due  to  a  striking 
increase  of  cells  in  the  capillaries  and  between  the  capillaries 
and  respiratory  epithelium.     The  majority  of  the  infiltrating 


148  WOLBACH. 

cells  are  large  mononuclear  (endothelial  cells),  a  few  of  which 
have  taken  up  red  blood  corpuscles  and  other  cells.  In  a 
few  places  about  veins  this  infiltration  is  very  marked,  and 
there  are  in  addition  to  the  endothelial  cells  many  poly- 
morphonuclear leucocytes  and  an  occasional  mast  cell.  One 
section  out  of  four  shows  a  few  small  veins  occluded  with 
coarse-meshed  fibrin  enclosing  polymorphonuclear  leucocytes 
and  mononuclear  phagocytic  cells  (endothelial  cells) ;  the  walls 
of  these  veins  contain  migrating  leucocytes.  One  large  vein 
contains  a  cluster  of  large  mononuclear  cells  attached  to  the 
endothelium.  No  parasites  are  demonstrable  in  these  lesions. 
The  arteries  show  no  lesions.  The  contents  of  arteries  and 
veins  include  a  large  number  of  mononuclear  (endothelial) 
phagocytic  cells.  There  is  a  moderate  amount  of  carbon  pig- 
ment in  the  connective  tissue  around  large  bronchi.  The 
cells  of  the  respiratory  epithelium,  where  the  alveolar  walls 
are  most  markedly  thickened,  are  cuboidal  in  shape. 

Spleen  (Fig.  62) :  The  spleen  is  tremendously  engorged 
with  blood,  and  there  are  small  areas  which  appear  simply 
as  pools  of  blood,  without  structure  of  the  spleen  remaining. 
The  absence  of  lymphoid  cells  in  the  reticular  tissue  of  the 
pulp  is  very  striking,  and  this  tissue  is  filled  with  red  blood 
corpuscles  and  mononuclear  phagocytic  (endothelial)  cells 
containing  red  blood  corpuscles,  polymorphonuclear  leucocytes 
and  nuclear  detritus.  Some  of  these  phagocytic  cells  contain 
six  to  a  dozen  red  blood  corpuscles  in  varying  stages  of  disin- 
tegration. Similar  phagocytic  cells  occur  in  great  abundance 
in  the  sinuses  (pulp  veins)  of  the  spleen,  and  in  the  smaller 
veins,  free  and  attached  to  the  walls.  There  are  numerous 
miliary  sized  collections  of  polymorphonuclear  leucocytes  in 
the  pulp,  in  regions  where  collections  of  phagocytic  cells  and 
sinus  walls  (pulp  veins)  are  necrotic.  There  are  a  few  large  cells 
of  the  lymphocyte  series  and  many  polymorphonuclear  leuco- 
cytes scattered  throughout  the  pulp.  The  Malpighian  bodies 
consist  of  small  collections  of  lymphoid  cells  about  the  central 
arteries,  and  show  no  lesions.  They  contain  no  foreign  cells 
and  show  no  evidence  of  activity  (or  germinal  centers).  The 
arteries  show  moderate  hyaline  change  and  thickening.     No 


ROCKY    MOUNTAIN    SPOTTED    FEVER.  1 49 

acute  lesions  can  be  found  in  arteries  or  veins.  The  capsule 
contains  numerous  migrating  polymorphonuclear  leucocytes. 
The  peritoneal  epithelium  is  swollen  and  cuboidal.  Careful 
searching  fails  to  reveal  parasites  of  any  sort  in  the  spleen. 

Liver  (Fig.  61):  The  organ  is  moderately  injected  through- 
out and  markedly  injected  about  the  central  (hepatic) 
veins.  There  is  slight  fat  vacuolation  of  the  liver  cells  in 
the  central  portion  of  the  lobules,  i.e.,  adjacent  to  the  hepatic 
veins.  The  sinusoids  contain  numerous  large  mononuclear 
phagocytic  (endothelial)  cells,  a  small  proportion  of  which 
contain  red  blood  corpuscles,  polymorphonuclear  leucocytes 
and  nuclear  material.  The  lining  cells  of  the  sinusoids 
(Kiipffer  cells)  are  swollen,  and  a  few  show  mitoses;  occasion- 
ally they  contain  red  blood  corpuscles  and  leucocytes.  The 
liver  cells  contain  an  increased  amount  of  greenish  granular 
pigment.  There  are  occasional  minute  necroses  of  the  liver 
columns,  usually  involving  one  to  a  few  liver  cells  and  shown 
by  a  hyaline,  deeply  eosin-staining,  cytoplasm,  pycnotic 
nuclei  and  invasion  by  polymorphonuclear  leucocytes.  The 
portal  spaces,  bile  ducts  and  arteries  and  veins  show  no 
lesions.  The  veins  contain  many  mononuclear  phagocytic 
cells  like  those  found  in  the  sinusoids. 

Pancreas:  There  is  a  considerable  increase  of  fibrous 
tissue  in  the  acini,  fairly  uniformly  distributed.  The  islands 
of  Langerhans  are  normal.  There  are  no  acute  lesions.  The 
blood  vessels  show  no  lesions;  they  contain  numerous  mono- 
nuclear leucocytes,  a  few  of  which  are  phagocytic.  The  ducts 
are  normal. 

Stomach:  Two  blocks  from  the  pyloric  end  were  exam- 
ined. The  mucosa,  submucosa  and  muscularis  of  both  the 
blocks  are  normal.  In  the  subserous  connective  tissue  from 
one  location  is  a  small  artery  with  a  mural  thrombus  composed 
of  fibrin,  platelets,  mononuclear  phagocytic  cells  and  a  few 
polynuclear  leucocytes.  This  thrombus  is  applied  to  about 
one  fourth  the  circumference  of  the  vessel.  The  wall  of  the 
artery  is  otherwise  normal.  No  other  vessel  lesions  are  to  be 
found. 


150  WOLBACH. 

Duodenum:  One  block  examined.  The  duodenum  shows 
no  lesions.  The  blood  vessels  are  normal.  Jejunum:  Two 
blocks  examined.  There  are  no  lesions.  The  blood  vessels 
are  normal.  Ileum:  Three  blocks  examined.  There  are  no 
lesions.  The  blood  vessels  are  normal.  Colon:  Two  blocks 
examined.  There  are  no  lesions.  The  blood  vessels  are 
normal. 

Kidney:  There  are  no  acute  lesions  of  the  kidney  or 
blood  vessels.  The  kidney  tissue  shows  a  few  areas  of  fibrosis 
containing  sclerosed  glomeruli.  The  arteries  show  slight 
arteriosclerotic  changes.  The  veins,  capillaries  and  glomeru- 
lar capillaries  are  normal. 

Adrenal:  The  adrenal  and  blood  vessels  and  the  surround- 
ing fat  and  blood  vessels  are  normal. 

Thyroid  gland :  The  thyroid  follicles  and  their  contents  are 
normal.  The  stroma  in  general  is  normal.  A  few  medium-sized 
veins  and  several  small  ones  show  acute  lesions.  The  larger 
veins  contain  mural  thrombi,  consisting  of  a  small  amount  of 
fibrin,  numerous  mononuclear  phagocytic  (endothelial)  cells 
and  polymorphonuclear  leucocytes.  The  endothelium  is 
swollen  adjacent  to  the  thrombi.  The  media  is  infiltrated 
with  polymorphonuclear  leucocytes.  In  the  attached  swollen 
endothelial  cells,  and  in  smooth  muscle  cells  of  the  media,  are 
numerous  exceedingly  minute  paired  and  single  organisms, 
usually  surrounded  by  a  clear  space  or  halo.  Some  smaller 
veins  and  a  few  capillaries  are  completely  occluded  with 
mononuclear  phagocytic  cells  and  polymorphonuclear  leuco- 
cytes. The  walls  are  heavily  infiltrated  with  polymorpho- 
nuclear leucocytes,  as  is  the  adjacent  connective  tissue.  In 
the  latter  location  there  are  numerous  large  mononuclear 
•cells  (endothelial  cells) ,  some  of  which  are  phagocytic.  Similar 
minute  parasites  occur  in  the  small  veins.  The  largest  forms 
■of  these  parasites  have  tapering  ends  and  have  about  one 
fourth  the  dimensions  of  the  pneumococcus.  The  pairs 
measure  slightly  less  than  one  micron  in  length,  the  estimated 
width  is  about  one  fourth  of  a  micron. 

Aorta:  The  aorta  shows  moderate  arteriosclerotic  changes. 
There  are  no  acute  lesions.  The  vasa  vasorum  show  no 
lesions. 


ROCKY    MOUNTAIN    SPOTTED    FEVER.  I51 

Lymph  nodes :  Axillary  nodes;  two  examined.  Both  lymph 
nodes  show  packing  of  the  lymph  sinuses  with  large  mono- 
nuclear phagocytic  cells  (endothelial  cells),  which  contain 
red  blood  corpuscles,  lymphoid  cells,  and  a  few  polymorpho- 
nuclear leucocytes.  The  endothelium  of  the  sinuses  is  swollen 
and  a  few  cells  in  situ  show  phagocytosis  of  the  cells  named 
above.  The  sinuses  contain  also  numerous  polymorpho- 
nuclear leucocytes,  a  rare  eosinophile  and  a  few  mast  cells. 
The  lymphoid  tissue,  i.e.,  secondary  follicles  and  medullary 
cords,  show  no  lesions.  The  blood  vessels  of  the  nodes  and 
adjacent  areolar  tissue  show  no  lesions. 

Inguinal  nodes:  Two  examined.  The  inguinal  nodes  are 
similar  to  the  axillary,  though  the  endothelial  cell  reaction 
is  more  marked,  as  there  are  very  many  phagocytic  cells  in 
the  medullary  cords.  The  secondary  follicles  are  small  and 
irregular  in  shape. 

Bronchial  nodes:  Two  examined.  These  nodes  show 
marked  carbon  pigmentation  and  small  numbers  of  phago- 
■cytic  cells  in  the  sinuses,  otherwise  they  are  negative.  The 
blood  vessels  of  the  surrounding  areolar  tissue  show^  no  lesions. 
Mesenteric  nodes :  Five  examined.  The  sinuses  are  packed 
with  phagocytic  cells  similar  to  those  of  the  peripheral  lymph 
nodes.  A  rare  sinus  is  filled  with  necrotic  phagocytic  cells 
and  polymorphonuclear  leucocytes.  A  small  vein  in  the 
medulla  of  one  lymph  node  contains  a  thrombus.  A  few  of 
the  secondary  follicles  in  all  nodes  contain  small  central 
whorls  of  large  flattened  mononuclear  cells  in  which  are  a  few 
polymorphonuclear  leucocytes. 

Testis  and  epididymis:  A  section  through  body  of  testis, 
tunica  albuginea  and  visceral  tunica  vaginalis.  The  semi- 
niferous tubules  are  normal  and  show  spermatogenesis. 
The  tunica  albuginea  and  tunica  vaginalis  are  normal.  There 
are  striking  lesions  of  large  and  small-sized  blood  vessels, 
arteries  and  veins,  and  a  few  oedematous  and  infiltrated  areas 
of  the  interstitial  tissues,  in  the  substance  of  the  testis.  There 
are  a  few  small  areas  of  completely  fibrosed  seminiferous 
tubules  surrounded  by  normal  interstitial  tissue.  The  lesions 
of  arteries  and  veins  vary  from  minute  foci  of  swelling  of  the 


152  .  WOLBACH. 

endothelium,  forming  groups  of  a  few  cells  to  mural  thrombi 
with  extensive  infiltration  of  the  vessel  wall  with  polymorpho- 
nuclear leucocytes.  In  the  arteries  small  lesions  consist  of  a 
collection  of  swollen  endothelial  cells,  overlying  a  fragmented 
internal  elastic  lamina,  beneath  which  are  endothelial  cells 
(large  mononuclear  cells)  and  polymorphonuclear  leucocytes. 
Large  lesions  are  covered  with  fibrin,  in  which  are  endothelial 
cells  and  polymorphonuclear  leucocytes,  overlying  the  internal 
elastic  lamina  which  is  usually  fragmented  and  deeply  stained 
with  the  basic  stain.  The  media  is  infiltrated  with  large 
mononuclear  cells,  and  polymorphonuclear  leucocytes.  In 
large  nlononuclear  cells  and  in  smooth  muscle  fibers  are  large 
numbers  of  minute  paired  round  and  ovoid  bodies,  which  stain 
blue  with  the  Giemsa  stain.  These  bodies  are  usually  sur- 
rounded by  a  clear  zone  or  halo.  The  length  of  the  largest 
pairs  of  ovoid  forms  is  slightly  less  than  one  micron,  while  the 
estimated  width  is  less  than  .25  micron.  The  packing  of 
these  parasites  in  smooth  muscle  cells  is  strikingly  seen  in 
tangential  sections  of  affected  arteries  and  veins  where  occa- 
sional cells  are  almost  completely  filled  with  them.  In  such 
instances,  the  nucleus  of  the  smooth  muscle  cell  stains  deeply 
and  homogeneously;  the  cytoplasm  occasionally  shows  hyaline 
change.  These  parasites  are  also  found  in  large  numbers  in 
endothelial  cells  lying  just  beneath  the  internal  elastic  lamina 
or  in  the  fibrin  above.  They  are  also  found  in  small  numbers 
in  the  endothelium  of  the  whole  circumference  of  the  vessels, 
and  in  the  endothelium  of  vessels  showing  no  reaction  other 
than  a  slight  swelling  of  the  endothelium  itself.  Small  veins 
and  capillaries  are  occasionally  found  completely  occluded 
by  fibrin  and  mononuclear  (endothelial)  cells  and  polymorpho- 
nuclear leucocytes.  Such  vessels  are  surrounded  by  collec- 
tions of  mononuclear  phagocytic  cells  (endothelial  cells)  in 
which  are  numerous  polymorphonuclear  leucocytes.  The 
minute  paired  organisms  are  also  found  in  these  lesions,  both 
within  the  lumen  of  the  vessel  and  in  endothelial  cells  in  the 
perivascular  zone  of  infiltration.  Occasional,  apparently  nor- 
mal capillaries  contain  a  few  pairs  of  the  organisms  in  the  lining 
endothelium. 


ROCKY   MOUNTAIN    SPOTTED    FEVER.  1 53 

Sections  through  the  testis  and  epididymis.  Four  blocks 
examined.  The  testis  shows  vascular  lesions  as  described 
above.  The  seminiferous  tubules,  tubules  of  the  rete,  the 
efferent  ducts  of  the  testis  and  the  ducts  of  the  epididymis 
are  all  normal.  There  is  considerable  oedema  of  the  con- 
nective tissue  of  the  epididymis;  and  between  the  separated 
connective  tissue  bundles  are  occasional  meshworks  of  delicate 
fibrin  strands,  lymphoid  cells,  plasma  cells  and  large  mono- 
nuclear cells,  some  of  which  are  phagocytic.  The  arteries  and 
veins  of  the  epididymis  (tunica  albuginea)  show^  thromboses 
and  endothelial  cell  proliferations  as  described  in  the  testis. 

Sections  through  the  testis,  pampiniform  plexus  and  ductus 
deferens.  Two  blocks  examined.  The  testis  and  its  blood 
vessels  are  similar  to  the  other  sections.  The  ductus  deferens 
shows  no  lesions.  Arteries  and  veins  of  the  plexus  of  all 
calibers  show  lesions  of  the  intima  and  mural  thrombosis, 
the  minute  paired  organisms  described  are  invariably  present 
in  the  vessels  showing  lesions.  In  large  veins  there  are  col- 
lections of  endothelial  cells  beneath  the  lining  endothelium, 
the  latter  forming  loops  to  enclose  the  cell  groups.  Some 
veins  of  medium  size  are  nearly  completely  occluded  by  these 
cells.  In  vessels  cut  longitudinally  showing  this  reaction, 
there  are  always  small  fibrin  thrombi  at  some  level;  the 
minute  parasites  are  found  in  these  vessels  in  endothelial  cells 
chiefly.  The  lymphatics  of  the  epididymis  and  the  plexus 
show  no  lesions;  a  few  contain  fair  numbers  of  phagocytic 
mononuclear  (endothelial)  cells. 

Section  through  the  ductus  deferens,  epididymis  and 
pampiniform  plexus.  Four  blocks  examined.  These  sections 
all  exhibit  the  same  extensive  lesions  of  the  blood  vessels  and 
constant  presence  of  the  minute  parasite. 

Prostate  gland:  The  glands  show  considerable  hyper- 
plasia. There  are  no  acute  lesions.  The  blood  vessels  show 
no  acute  lesions.  Bladder:  Normal.  The  blood  vessels  are 
normal. 

Brain:  Cerebral  cortex.  Blocks  from  the  frontal,  para- 
central, occipital  and  temporal  regions  were  preserved.  The 
pia  arachnoid   in  all  the  above  regions  shows  evidences  of 


154  WOLBACH. 

oedema  in  the  wide  separation  of  the  connective  tissue  fibers 
and  in  the  presence  of  a  few  lymphoid  cells,  and  a  rare  poly- 
morphonuclear leucocyte,  red  blood  corpuscle  and  amoeboid 
phagocytic  cells.  The  brain  cortex  and  vessels  show  no 
lesions.  The  vessels  are  markedly  injected  with  blood. 
Single  veins  in  each  of  two  regions  —  paracentral  and  occipital 
—  show  minute  lesions  of  the  intima  in  the  form  of  collections 
of  mononuclear  cells  (endothelial  cells)  a  few  of  which  are 
phagocytic  and  polymorphonuclear  leucocytes  on  the  surface 
of  the  intima  and  in  the  wall  of  the  vessel. 

Cerebellum:  Two  blocks  examined;  in  one  a  single  small 
-artery  shows  a  minute  lesion  —  a  thin  deposit  of  fibrin  and  a 
few  endothelial  cells  attached  to  the  intima,  in  which  are  a 
few  pairs  of  the  minute  organism.  The  cerebellar  tissue  is  free 
from  lesions.  The  blood  vessels  of  the  substance  of  the 
cerebellum  show  no  lesions.     The  meninges  are  normal. 

Medulla  and  pons:  Sections  through  the  medulla  and 
floor  of  fourth  ventricle  show  no  lesions  of  nerve  tissue  or 
blood  vessels.  A  section  through  the  pons  and  meninges 
shows  no  lesions  of  blood  vessels  or  nervous  tissue. 

Skin  (Figs.  60,  66  and  68) :  Blocks  were  taken  from  the 
skin  of  the  neck  (tick  bite),  axilla  (tick  bite),  arm,  abdomen, 
back,  buttock,  thigh,  legs  and  ankles. 

Skin  of  neck,  including  tick  bite;  subcutaneous  fat  and 
muscle:  The  epidermis  is  missing  over  the  lesion  of  the  tick 
bite,  where  there  is  a  fibrinous  crust  several  millimeters  long. 
The  corium  projects  above  the  level  of  the  epidermis  and  is 
completely  necrotic  in  an  irregular  but  sharply  delineated 
area,  which  consists  of  bundles  of  hyaline  collagen  fibrils  and 
basic  staining  elastic  fibers  widely  separated  by  necrotic  cells 
and  detritus.  The  necrotic  area  is  several  millimeters  long 
and  extends  downwards  for  about  half  the  thickness  of  the 
skin.  At  the  periphery  of  the  necrotic  area  there  is  a  small 
amount  of  fibrin  and  numbers  of  red  blood  corpuscles  between 
the  collagen  bundles,  as  well  as  many  polymorphonuclear 
leucocytes  and  a  few  mononuclear  phagocytic  cells  (endothelial 
cells).  Running  into  the  necrotic  area  are  several  thrombosed 
necrotic  walled  arteries  and  veins,  while  surrounding  adjacent 


ROCKY    MOUNTAIN    SPOTTED    FEVER.  1 55 

coil  glands  there  are  heavy  zones  of  lymphoid  and  plasma  cell 
infiltration  in  which  are  numerous  large  mononuclear  cells, 
some  of  them  phagocytic. 

The  epidermis  shows  no  change,  except  at  the  edge  of  the 
tick  bite,  where  it  is  thinned,  as  with  any  ulceration  of  the 
skin.  The  corium  everywhere  contains  a  few  wandering  cells, 
mostly  large  mononuclear  amoeboid  cells,  many  containing 
brown,  granular  pigment.  The  blood  vessels  of  the  corium, 
subcutaneous  tissue  and  muscle  show  striking  changes,  in  the 
form  of  lesions  of  the  intima,  and  thrombosis.  Many  of  the 
papillary  capillaries  are  occluded  by  polymorphonuclear  leuco- 
cytes and  mononuclear  phagocytic  cells  (endothelial  cells), 
and  are  surrounded  by  zones  of  large  mononuclear  cells  and 
polymorphonuclear  leucocytes. 

Capillaries  about  the  coil  glands  show  similar  lesions  and 
perivascular  infiltrations.  Arteries  and  veins  show  lesions 
similar  to  those  described  in  testis  and  pampiniform  plexus, 
in  corium,  subcutaneous  fat  and  muscle.  The  mural  thrombi 
are  most  marked  in  the  larger  size  arteries  of  the  lower  layer 
of  the  corium  and  subcutaneous  tissue.  Many  fat  cells  in 
the  subcutaneous  fat  lobules  are  shrunken,  filled  with  granular 
material  and  surrounded  by  a  layer  of  cuboidal  epithelioid 
cells  (endothelial  cells),  or  narrow,  crescentic  multinuclear 
cells  (giant  cells).  Between  the  fat  cells  are  many  similar 
cells  and  a  few  cells  undergoing  mitoses.  The  minute  paired 
organisms  described  in  lesions  of  other  blood  vessels  occur  in 
this  region  in  capillaries  with  swollen  endothelium,  and  in 
vessel  walls  with  lesions  within  smooth  muscle  cells  and 
endothelial  cells. 

Skin  of  axilla  with  tick  bite :  These  sections  present  identi- 
cal lesions  with  those  from  the  neck. 

Skin  of  arms:  The  epidermis,  coil  glands,  sebaceous  glands 
and  hair  follicles  are  normal.  There  are  a  few  arteries  and 
veins  in  the  deeper  layer  of  the  corium,  with  mural  thrombi 
and  infiltrated  walls.  Numerous  capillaries  of  the  papillae 
and  vessels  of  the  subpapillary  plexus  are  filled  with  mono- 
nuclear cells  (endothelial  cells),  and  surrounded  by  zones  of 
similar  cells.  Parasites  are  present  in  the  vessel  lesions  as  in 
the  other  sections. 


156  WOLBACH. 

Skin  of  abdomen:  The  papillary  capillaries  are  practically 
normal;  they  contain  numerous  large  mononuclear  cells.  The 
epidermis  and  appendages  are  normal.  A  single  large  artery 
just  below  the  corium  is  almost  completely  occluded  by  a 
coarse-meshed  hyaline  fibrin  thrombus,  which  has  left  a  small 
eccentrically  situated  lumen,  in  part  bounded  by  the  vessel 
wall.  The  whole  wall  of  the  artery  is  infiltrated  with  polymor- 
phonuclear leucocytes.  The  muscle  fibers  of  the  media  in  a 
small  area  are  necrotic  and  the  fibrin  strands  of  the  thrombus 
are  continuous  with  fibrin  in  the  media.  The  thrombus  con- 
tains but  few  cells,  polymorphonuclear  leucocytes  and  large 
mononuclear  phagocytic  cells  (endothelial  cells).  The  endo- 
thelium of  the  artery  is  not  distinguishable,  as  the  hyaline 
fibrin  lies  upon  the  elastica  or  extends  beneath  it.  Surround- 
ing the  artery  in  the  adventitia  is  a  zone  of  large  mononuclear 
phagocytic  cells  and  polymorphonuclear  leucocytes  with  a 
small  amount  of  fibrin.  In  the  subcutaneous  fat  are  several 
smaller  vessels  showing  less  advanced  lesions.  The  minute 
parasite  is  present  in  small  numbers  in  all  the  affected  vessels. 

Skin  of  thigh :  There  are  lesions  of  the  subcutaneous  arteries 
with  mural  thrombi  and  occluding  thrombi.  The  minute 
parasites  are  present  in  the  vessel  walls.  The  capillaries  of 
the  skin  show  slight  lesions  only. 

Skin  of  buttock:  The  lesions  of  the  deeper  arteries  of  corium 
and  subcutaneous  fat  are  identical  with  those  from  the  thigh. 

Skin  of  leg  and  ankle:  There  are  numerous  thrombosed 
arteries  in  the  subcutaneous  tissue.  The  capillaries  of  the 
corium  show  lesions  similar  to  those  described  above.  In 
one  section  of  skin  from  the  leg  there  is  hemorrhage  into 
several  fat  lobules.  The  parasites  are  present  as  in  the  lesions 
from  other  locations. 

Skin  of  scrotum:  There  is  a  more  uniform  involvement 
of  the  blood  vessels  of  the  skin  and  dartos  than  in  skin 
from  any  other  location.  Vessels  of  all  calibers  are  the  seat 
of  acute  lesions  and  thromboses.  There  are  many  small 
arteries  and  veins  showing  early  thromboses  with  enormous 
numbers  of  the  minute  parasites  in  smooth  muscle  fibers  and 
n  endothelial  cells.     The  lesions  vary  in  size  and  age,  and 


ROCKY   MOUNTAIN    SPOTTED    FEVER.  1 57 

conform  to  the  lesions  of  the  vessels  of  the  pampiniform  plexus, 
testicle  and  epididymis.  The  epidermis  in  a  few  places 
shows  a  heaping-up  of  the  horny  layer  and  thinning  of  under- 
lying layers  over  lesions  of  the  corium  consisting  of  oedematous 
areas  containing  much  finely  granular  material  and  large 
numbers  of  closely  packed  cells,  mononuclear  leucocytes,  and 
lymphoid  cells.  In  such  areas  are  capillaries  occluded  with 
large  mononuclear  cells  and  polymorphonuclear  leucocytes 
and  fibrin.  These  areas  suggest  beginning  necrosis  of  the 
skin. 

Fat  stain.  Scharlach  R.  —  Heart:  No  fat.  A  large 
amount  of  lipochrome  perinuclear  pigment.  Spleen:  No  fat. 
Liver:  Small  amount  of  fat  about  centers  of  lobular,  i.e., 
hepatic  veins,  in  small  droplets.  Kidneys:  An  occasional 
convoluted  tubule  contains  numerous  small  fat  drops. 
Adrenal:  Contains  much  less  than  normal  amount  of  lipoid 
material,  the  greater  portions  contain  only  an  occasional 
droplet,  but  here  and  there  in  the  fascicular  zone  are  areas  of 
dense  red  coloration  due  to  cells  packed  with  lipoid  droplets. 

Case  III.  —  The  clinical  data  on  this  case  are  meager;  it  is  that  of  a 
Finnish  laborer,  31  years  old,  who  worked  in  the  vicinity  of  Darby,  Mont., 
in  the  southern  (upper)  end  of  the  Bitter  Root  Valley.  He  was  unable 
to  speak  English,  but  his  illness  was  noticed  first  on  May  12.  The  week 
previous,  while  at  Darby,  three  ticks  were  known  to  have  been  attached 
on  his  leg  and  thigh.  His  first  complaints  were  those  of  fever  and  aches. 
He  was  nauseated  and  vomited  the  day  before  admission  to  the  Thornton 
Hospital  at  Stevensville,  Mont. 

He  had  a  fine,  punctate,  erythematous  rash  all  over  his  body  when 
admitted  the  evening  of  May  17,  five  days  after  the  onset.  The  rash  on 
May  18  was  most  marked  on  the  ankles,  legs  and  buttocks.  On  the 
evening  of  May  18  he  became  delirious  and  developed  a  cough  without 
sputum.  On  May  19  the  rash  was  more  pronounced  but  still  disappeared 
upon  pressure.  ,A  distinct  yellowish  cast  to  the  skin  appeared.  The 
tongue  was  swollen,  dry,  bright  red  at  the  edges,  with  a  heavy  white  coat- 
ing over  the  middle  and  posterior  portions.  A  transfusion  of  450  c.c.  of 
citrated  blood  was  given  from  an  immune  donor. 

On  May  20,  in  the  early  morning,  he  became  unconscious.  The  skin 
was  now  of  a  distinct  yellowish  color,  and  was  mottled  dull  red  over  the 
whole  body.  These  dull  red  areas  increased  in  size  during  the  day  and 
ranged  from  a  few  centimeters  to  areas  10  x  25  cm.  in  diameter  over  the 
lower  portions  of  the  thighs.  On  stroking  these  areas  with  the  fingernail 
the  dusky  lividity  blanched  after  an  interval  of  about  five  seconds,  leav- 
ing a  broad  pale-yellow  line  in  which  the  papilla  became  slowly  erect. 


158 


WOLBACH. 


This  condition  persisted  for  about  a  minute.  During  the  day  deep- 
seated  red  spots  i  to  2  mm.  in  diameter,  which  did  not  disappear  upon 
pressure,  appeared  on  the  elbows  and  buttocks.  The  pulse  became  very 
rapid  and  feeble,  the  respirations  rapid,  and  the  death  occurred  at  8.40 

P.M. 

Differential  blood  counts  made  in  the  sixth  and  seventh  days  of  the 
disease  are  recorded  on  page  32. 


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Charts  of  temperature,  pulse  and  respiration  of  Case  III.     Male,  age  31 
years.     Death  on  eighth  day  of  disease. 


Two  guinea-pigs  were  inoculated  May  18,  one  with  one 
cubic  centimeter,  the  other  with  two  cubic  centimeters  of 
blood  in  citrate  saline  solution.  Both  developed  the  typical 
temperatures  and  lesions  of  spotted  fever,  and  upon  these 
guinea-pigs  ticks  were  fed  which  afterwards,  in  Boston,  com- 
municated the  disease  to  another  guinea-pig.  See  record  of 
Ticks  XXXIII.  and  XXXIV.,  page  96. 


ROCKY    MOUNTAIN    SPOTTED    FEVER.  1 59 

Autopsy.  Spotted  fever  Case  III.  Hamilton,  Mont., 
May  20,  1917,  at  9.30  p.m.  (By  tungsten  light.)  One  hour 
post-mortem. 

Body:  Is  that  of  a  well-developed,  muscular,  well-nour- 
ished white  man  about  165  centimeters  long.  Rigor  mortis 
is  beginning  in  arms  and  legs.  Body  heat  present.  The 
skin  everywhere  is  dusky  reddish-yellow  in  color,  and  is 
mottled  with  large,  irregular  areas  of  deeper  dull  red.  Over 
the  lower  legs,  arms,  chest  and  thighs  a  fine  red  rash  is  present, 
which  disappears  on  pressure.  The  back  and  buttocks  are 
bright  red  in  color,  due  to  post-mortem  lividity(?).  The 
buttocks  are  mottled  with  deep  red-colored  areas,  which  do 
not  disappear  upon  pressure,  .2  to  .5  centimeter  in  diameter. 
The  lower  part  of  the  right  half  of  the  scrotum  is  deep  red 
in  color.  There  is  no  oedema.  The  pupils  are  equal,  .2  centi- 
meter in  diameter.  The  sclerae  are  deeply  injected.  Cornea 
clear  and  firm.  On  incision  through  the  skin  over  the  chest, 
back,  thighs,  abdomen,  legs  and  ankles  the  subcutaneous  fat 
is  found  injected  with  blood  in  small  areas,  and  there  are 
occasional  small  areas  of  fat  which  are  colored  reddish.  The 
fascia  lata  and  the  tendon  sheaths  of  the  ankles  are  injected, 
and  the  overlying  tissues  of  each  are  yellowish  in  color  and 
contain  free  liquid  (oedema). 

Peritoneal  cavity:  The  peritoneal  surfaces  are  everywhere 
smooth,  moist,  glistening;  there  is  no  free  liquid.  No  ad- 
hesions. The  appendix  is  normal.  The  mesenteric  lymph 
nodes  are  small,  pale  in  color,  normal  in  consistency. 

Chest  cavities:     Inspected   through  the  diaphragm.     The 
left  lung  along  the  outer  border  of  the  lower  lobe  is  adherent 
to  the  chest  wall  by  loose,  tough  fibrous  tissue.     The  right  lung . 
is  free  from  adhesions.     No  free  liquid  in  either  cavity. 

Pericardial  cavity:  Normal.  No  excess  of  liquid  or  exu- 
date. 

Heart:  The  left  ventricle  is  contracted.  The  right  ven- 
tricle is  patulous,  and  the  heart  contains  a  few  small,  soft 
cruor  clots  and  dark  red  liquid  blood.  The  heart  is  normal 
in  size.  The  valves  and  endocardium  are  normal.  There  are 
a  few  yellowish  areas,  found  on  section,  in  the  myocardium,. 


l60  WOLBACH. 

particularly  in  the  interventricular  septum  along  the  left 
border  and  adjacent  wall  of  the  left  ventricle. 

Lungs:  Both  lungs  are  voluminous,  pink,  with  consider- 
able black  pigment  distributed  beneath  the  pleura  in  the 
interlobular  septa.  Both  lungs  are  soft,  crepitant  throughout. 
On  section  the  cut  surfaces  are  dry;  the  vessels  yield  con- 
siderable dark  red  fluid  blood. 

Spleen:  The  spleen  is  markedly  enlarged,  size  lO  by  8  by 
6  centimeters.  The  edges  are  rounded.  The  capsule  is  tense, 
color  dark  bluish-red.  On  section  the  cut  surfaces  are  very 
dark  red.  The  trabeculae  and  splenic  corpuscles  are  not 
visible.  The  cut  surfaces  are  firm,  and  yield  blood  on  scrap- 
ing.    The  consistency  is  firm,  resilient. 

Liver:  Normal  in  size;  estimated  weight,  1600  grams. 
The  color  is  brownish-red.  Consistency  normal.  On  section 
the  lobules  are  faintly  indicated  by  a  paler  reddish  tracery. 
Gall  bladder  and  ducts  negative. 

Gastro-intestinal  tract:  The  stomach  is  contracted.  The 
mucosa  is  flecked  with  small  particles  of  brown  granular 
material,  free  on  the  surface,  and  is  considerably  injected. 
The  small  intestines  and  colon  are  normal  in  appearance. 

Pancreas:     Normal  in  size,  color  and  consistency. 

Kidneys:  Normal  in  size.  Estimated  weight,  300  grams. 
There  is  pronounced  foetal  lobulation  of  both.  In  the  outer 
surface  of  the  right  kidney  is  a  cysto  e  centimeter  in  diameter, 
filled  with  clear,  colorless  liquid.  The  cortex  averages  .6  to 
.7  centimeter  in  width,  and  is  grayish-red  in  color.  The 
glomeruli  are  visible  as  colorless  points.  The  pyramids  are 
brownish-red  in  color,  normal  in  appearance. 

Adrenal  glands:  Normal  in  size,  color  and  consistency, 
except  for  a  few  small  bright  yellow  nodules  two  or  three 
millimeters  in  diameter  in  the  cortex  of  the  left  adrenal. 

Genitalia:  The  subcutaneous  tissues  of  the  scrotum  are 
wet  and  deeply  injected,  and  in  the  right  side  there  are  areas 
of  dark  red,  due  to  extravasation  of  blood.  The  testes  are 
moderately  injected,  the  epididymis  swollen,  wet  and  deeply 
injected.  Testes  on  section  are  normal  in  appearance.  The 
epididymes  show  dark  red  punctate  areas. 


ROCKY    MOUNTAIN    SPOTTED   FEVER.  l6l 

Inguinal  lymph  nodes:  Are  large,  the  largest  measuring 
1.5  by  I  by  .5  centimeters.     All  are  purplish-gray  and  firm. 

Anatomical  diagnoses.  —  Generalized  subcutaneous  extrava- 
sations of  blood.  Hematogenous  pigmentation  of  the  skin. 
Acute  splenitis.     Acute  epididymitis. 

Spotted  fever  Case  III.  Microscopic  description.  Eosin- 
methylene-blue  and  Giemsa  stains.  —  Heart:  A  section 
through  the  base  of  the  anterior  group  of  papillary  muscles 
and  ventricle  wall.  The  muscle  fibers  of  the  ventricle  wall 
show  nothing  abnormal.  The  fibers  of  the  papillary  muscle 
show  in  places  a  delicate  vacuolization.  There  are  also  a  few 
small  groups  of  large  amoeboid  mononuclear  cells  and  lym- 
phocytes between  muscle  fibers,  or  grouped  about  capillaries. 
The  blood  vessels,  including  those  of  the  pericardium,  show  no 
change.     The  endocardium  shows  nothing  abnormal. 

Lungs:  There  is  moderate  injection  of  the  blood  vessels, 
no  exudate.  In  the  blood  vessels,  and  in  the  alveolar  walls, 
are  large  numbers  of  large  mononuclear  cells  (endothelial  cells), 
a  few  of  which  contain  red  blood  corpuscles  and  nuclear  de- 
tritus. There  are  no  lesions  of  the  blood-vessel  walls.  The 
respiratory  epithelium  in  a  few  places  is  replaced  by  a  cuboidal 
type  of  cell.  There  are  a  few  areas  of  marked  carbon  pig- 
mentation about  large  blood  vessels  and  adjacent  to  the 
bronchi,  accompanied  by  the  usual  fibrosis.  The  bronchi  are 
free  from  exudation.  In  the  larger  bronchi  the  epithelium 
contains  a  considerable  amount  of  coarsely  granular  greenish 
pigment,  situated  in  the  distal  side  of  the  nuclei  in  the  cells. 

Spleen:  The  spleen  is  tremendously  engorged  with  blood, 
with  small  areas  of  hemorrhage  into  the  pulp.  The  splenic 
corpuscles  are  small,  in  many  instances  being  mere  fringes  of 
lymphoid  cells  around  the  central  vessels.  They  contain  few 
mitotic  cells,  and  cells  of  the  germinal  center  type  are  almost 
wholly  absent.  The  central  vessels  are  normal,  and  there  is 
no  exudate  or  collection  of  large  cells  such  as  occur  in  diph- 
theria and  other  toxic  diseases.  The  splenic  pulp  has  under- 
gone striking  changes.  The  lymphoid  cells  in  the  reticular 
tissue  have  almost  wholly  disappeared;    in  their  places  are 


1 62  WOLBACH. 

red  blood  corpuscles,  polymorphonuclear  leucocytes,  and  large 
mononuclear  phagocytic  cells  (endothelial  cells),  many  filled 
to  distention  with  red  blood  corpuscles,  others  containing  in 
addition  lymphoid  cells,  polymorphonuclear  leucocytes  and 
densely  staining  nuclear  remains.  The  polymorphonuclear 
leucocytes  in  a  few  areas  appear  in  excess  of  other  cells,  but 
in  general  the  predominating  cells  are  red  blood  corpuscles 
and  the  phagocytic  cells.  The  sinuses  contain  a  large  num- 
ber of  phagocytic  cells  (endothelial  cells),  similar  to  those  in 
the  reticular  tissue,  and  many  swollen  cells  attached  to  the 
sinus  walls  contain  red  blood  corpuscles,  chromatin  detritus 
and  polynuclear  leucocytes.  The  veins  contain  many  phago- 
cytic cells  similar  to  those  described.  The  walls  of  arteries 
and  veins  show  no  lesions.  The  connective-tissue  structures, 
i.e.,  trabeculae  and  capsule,  show  no  lesions.  The  peritoneal 
cells  on  the  surface  of  the  spleen  are  swollen  and  cuboidal  in 
shape. 

Liver:  The  sinusoids  and  larger  blood  vessels  contain  only 
a  small  amount  of  blood.  The  liver  cells  show  slight  fat 
vacuolization  at  the  periphery  of  the  lobules.  There  are 
occasional  minute  focal  necroses  involving  single  or  very  small 
groups  of  liver  cells,  evidenced  by  a  change  in  staining  to  a 
deep  eosin  color  of  the  cells,  loss  of  nuclei  and  invasion  by 
polymorphonuclear  leucocytes.  A  single  large  area  of  necro- 
sis, involving  an  area  about  one  fourth  the  radius  of  a 
lobule,  was  found.  In  this  area  the  liver  columns  are  com- 
pletely disorganized  and  there  are  many  polymorphonuclear 
leucocytes  and  large  phagocytic  cells  (endothelial  cells), 
containing  red  blood  cells  and  nuclear  detritus.  The  liver 
cells  in  general  are  normal  in  appearance;  a  few  show  con- 
siderable brownish  granular  pigment.  The  sinusoids  contain 
many  mononuclear  phagocytic  cells  (endothelial  cells),  mostly 
containing  red  blood  cells,  a  few  polymorphonuclear  leuco- 
cytes and  chromatin  particles.  The  lining  cells  of  the  sinu- 
soids (Kiipffer  cells)  in  many  places  are  swollen,  and  contain 
red  blood  corpuscles  and  nuclear  detritus;  these  cells  often 
show  several  processes  when  situated  at  the  forking  of  columns 
of   liver   cells.     The   larger   blood   vessels   are   normal.     The 


ROCKY    MOUNTAIN    SPOTTED   FEVER.  1 63 

branches  of  the  portal  veins  contain  phagocytic  cells  (endo- 
thelial cells)  in  numbers  almost  equal  to  those  in  the  veins 
of  the  spleen.  The  bile  passages  are  normal.  The  connective 
tissue  of  the  portal  spaces  contains  a  few  polymorphonuclear 
leucocytes,  and  an  occasional  branch  of  a  portal  vein  shows 
polymorphonuclear  leucocytes  migrating  through  their  walls. 
The  arteries  and  veins  show  no  lesions.  The  capsule  and 
peritoneum  show  no  lesions. 

Pancreas:  The  pancreas  and  its  blood  vessels  are  normal. 
Adjacent  fat  tissues  and  blood  vessels  are  normal.  The 
larger  veins  of  the  pancreas  contain  numerous  mononuclear 
phagocytic  cells  (endothelial  cells)  similar  to  those  in  the 
vessels  of  liver  and  spleen.  Sections  of  the  pancreatic  artery 
show  no  lesions. 

Stomach:  Three  blocks  examined.  The  blood  vessels  of 
the  submucosa  are  markedly  injected.  The  mucosa  is  normal 
except  for  an  occasional  capillary  distended  with  polymorpho- 
nuclear leucocytes  and  phagocytic  mononuclear  (endothelial) 
cells.  An  occasional  lymphoid  follicle  contains  many  poly- 
morphonuclear leucocytes.  One  small  vein,  traversing  the 
muscularis  mucosae,  contains  a  small  mural  thrombus  composed 
of  granular  material,  polymorphonuclear  leucocytes  and  endo- 
thelial cells.  The  vein  wall  at  this  point  is  infiltrated  with 
polymorphonuclear  leucocytes.  A  few  small  arteries  in  the 
submucosa  show  the  earliest  possible  signs  of  a  reaction, 
swollen  endothelium  and  an  occasional  polymorphonuclear 
leucocyte  in  the  wall.  In  several  such  arteries  minute  paired 
and  single  oval  microorganisms  can  be  seen  (Giemsa  stain) 
lying  beneath  the  internal  elastic  lamina,  and  in  the  endothe- 
lium. Those  lesions  in  the  vessels  would  easily  escape  notice 
unless  specifically  looked  for.  The  muscularis  and  serosa  are 
normal. 

Small  intestine,  jejunum,  and  upper  part  of  ileum:  Four 
blocks  examined.  No  lesions  of  the  small  intestine  and  their 
blood  vessels  can  be  found.  A  few  veins  in  the  submucosa  of 
the  jejunum  contain  large  numbers  of  large  mononuclear 
leucocytes,  a  few  of  which  are  phagocytic  and  contain  red 
blood  cells  and  nuclear  remains. 


1 64  WOLBACH. 

Kidney:  There  Is  marked  injection  with  blood.  A  few 
glomeruli  show  accumulations  of  large  mononuclear,  occa- 
sionally phagocytic  (endothelial)  cells  in  the  capillaries ;  there 
are  also  occasional  polymorphonuclear  leucocytes  in  these 
collections  of  cells.  The  capsular  spaces  contain  small 
amounts  of  granular  material.  The  tubules  throughout  the 
sections  show  slight  dilatation, and  contain  circular  reticulum 
and  granular  detritus.  Many  collection  tubules  contain 
coarsely  granular  casts.     The  blood  vessels  show  no  lesions. 

Adrenal:  There  is  but  little  vacuolization  of  the  cells  of 
all  zones.  In  the  reticular  zone,  the  cells  of  which  stain 
solidly  for  the  most  part,  there  are  abrupt  transitions  to 
greatly  vacuolated  cells  which  are  separated  from  one  another. 
In  a  few  such  areas  there  are  many  polymorphonuclear  leuco- 
cytes, and  a  rare  phagocytic  mononuclear  cell  (endothelial  cell) , 
while  the  adrenal  cells  show  evidence  of  necrosis  in  staining 
reactions  and  by  invasion  with  leucocytes.  In  the  medulla 
there  are  a  few  areas  of  lymphoid  and  plasma  cell  infiltration. 
The  blood  vessels  show  no  lesions.  Superior  mesenteric 
artery:     A  cross  section  taken  near  its  origin  shows  no  lesions. 

Lymph  nodes:  Inguinal  nodes;  three  examined.  The 
sinuses  are  filled  with  large  mononuclear  cells  (endothelial 
cells),  many  of  which  are  phagocytic  and  contain  red  blood 
corpuscles,  lymphoid  cells  and  nuclear  detritus.  The  second- 
ary follicles  are  small,  distinguishable  with  difificulty  from  the 
medullary  cords;  a  few  show  central  collections  of  large 
mononuclear  cells;  some  are  flattened  and  concentrically 
arranged,  others  are  rounded  and  phagocytic.  Such  groups 
contain  numerous  polymorphonuclear  leucocytes.  The  medul- 
lary cords  contain  a  few  phagocytic  cells  and  eoslnophlles. 
The  blood  vessels  show  no  lesions. 

Mesenteric  nodes:  The  mesenteric  node  Is  similar  to  the 
inguinal  nodes  in  the  presence  of  phagocytic  mononuclear 
cells  in  the  sinuses;  they  are,  however,  less  numerous,  and 
there  are  fewer  red  blood  corpuscles  free  or  within  cells. 

Retroperitoneal  nodes  —  from  the  region  of  the  coeliac 
axis:  The  sinuses  are  greatly  distended,  and  filled  with  many 
mononuclear  phagocytic  cells    (endothelial   cells),   numerous 


ROCKY   MOUNTAIN    SPOTTED    FEVER.  165 

red  blood  corpuscles  and  lymphoid  cells,  a  few  polymorpho- 
nuclear leucocytes  and  an  occasional  mononuclear  eosinophile. 
Many  of  the  phagocytic  cells  contain  one  to  several  red 
blood  cells,  brownish  pigment,  and  often  lymphoid  cells  and 
polymorphonuclear  leucocytes.  Large  cells  attached  to  the 
sinus  walls  are  also  phagocytic  for  the  above  elements. 
There  is  a  small  amount  of  brown  granular  pigment  in  the 
medullary  cords,  within  cells. 

Skeletal  muscle  from  the  thigh:  A  few  muscle  fibers  show 
hyaline  change  and  loss  of  striations  comparable  to  those  in 
typhoid.  In  a  few  fibers  the  hyaline  change  is  sharply  de- 
lineated by  a  transverse  fracture,  possibly  artefact.  The 
nuclei  of  the  sarcolemma  show  no  change.  There  is  moderate 
oedema  and  infiltration  of  the  connective  tissue  accompanying 
blood  vessels  (internal  perimysium),  and  marked  lesions  of 
many  blood  vessels  of  all  sizes,  some  of  which  are  completely 
thrombosed.  The  smallest  lesions  of  the  vessels  consist  of 
groups  of  endothelial  cells  attached  to  the  intima.  In  arteries 
such  groups  overlie  swollen  and  fragmented  portions  of  the 
internal  elastic  lamina,  and  the  media  is  usually  infiltrated 
with  polymorphonuclear  leucocytes  and  large  mononuclear 
amoeboid  cells  (endothelial  cells).  The  muscle  fibers  of  the 
media  adjacent  to  the  lesion  of  the  intima  are  swollen,  and 
in  small  arteries  swollen  fibers  are  found  throughout  the 
circumference.  In  these  swollen  arteries,  in  endothelial  cells, 
and  occasionally  lying  apparently  free  above  and  below  the 
elastica,  are  large  numbers  of  minute  paired  ovoid  organisms. 
Occasionally,  spherical  masses  of  the  organisms  occur,  as  if 
completely  filling  an  endothelial  cell,  while  smooth  muscle 
fibers  are  often  completely  filled  with  them.  These  organisms 
are  surrounded  each  by  a  clear  zone  or  halo,  and  when  in 
compact  masses  seem  to  be  embedded  in  reddish  staining 
material  (Giemsa  stain).  The  largest  pairs  show  tapering  of 
the  distal  ends,  and  measure  slightly  less  than  one  micron  in 
length  for  the  pair.  The  estimated  width  (with  micrometer 
ocular)  is  about  one  fourth  of  a  micron.  The  lesions  in  veins 
are  similar  to  those  in  arteries;  endothelial  cell  proliferation* 
degeneration   of    the   intima   and    infiltration   of    the   media* 


1 66  WOLBACH. 

In  vessels  apparently  normal,  high  power  examination  reveals 
swollen  endothelial  cells  of  the  intima  enclosing  the  organisms 
described.  More  advanced  lesions  consist  of  fibrin  deposits 
which  occur  as  mural  thrombi,  or  as  occluding  thrombi, 
according  to  the  extent  of  the  lesion  of  the  vessel  wall.  Small- 
sized  veins  and  capillaries  are  completely  occluded  by  packed 
masses  of  phagocytic  cells  (enclosing  red  blood  corpuscles, 
polymorphonuclear  leucocytes  and  nuclear  detritus)  and 
polymorphonuclear  leucocytes.  Surrounding  small  vessels 
with  lesions  there  are  zones  of  large  mononuclear  cells  (en- 
dothelial), some  of  which  are  phagocytic  and  polymorpho- 
nuclear leucocytes.  Small  dilated  veins  often  contain  many 
phagocytic  endothelial  cells,  free  in  the  lumen,  and  rarely 
these  cells  contain  one  or  several  pairs  of  the  minute  organisms. 
The  oedematous  connective  tissue  septse  contain  a  few  large 
mononuclear  cells,  some  phagocytic,  some  amoeboid,  and  a 
rare  mast  cell. 

Testis,  epididymis,  and  pampiniform  plexus  (Figs.  51,  58 
and  63):  (i)  Section  through  testis  and  epididymis.  The 
testis  shows  no  lesions  of  the  seminiferous  tubules  or  inter- 
stitial tissue.  The  former  are  actively  spermatogenic.  There 
are  no  large  blood  vessels  In  the  sections.  A  few  small  arteries 
and  veins  show  swollen  endothelial  cells  and  polymorphonu- 
clear leucocytes  in  the  walls.  These  lesions  would  escape 
notice  unless  specifically  searched  for.  The  swollen  endo- 
thelium contains  numerous  pairs  of  organisms  like  those  found 
in  the  vessels  of  the  muscle.  The  tubules  of  the  epididymis 
and  the  ductus  deferens  show  no  lesions.  The  blood  vessels 
of  the  tunica  albuginea  and  pampiniform  plexus  show  widely 
distributed  and  very  striking  lesions,  in  arteries,  veins  and 
capillaries.  These  lesions  vary  from  small  clusters  of  large 
mononuclear  cells  attached  to  the  intima  and  accompanied 
by  Infiltration  of  the  media  with  polymorphonuclear  leuco- 
cytes, to  large  mural  thrombi  of  fibrin  and  cells  overlying 
extensive  necrosis  of  the  media.  In  medium-sized  veins  there 
are  festoon-like  loops  of  the  vascular  endothelium,  enclosing 
large  phagocytic  mononuclear  cells  and  polymorphonuclear 
leucocytes   and   occasionally   necrotic   phagocytic   cells,   and 


ROCKY   MOUNTAIN    SPOTTED    FEVER.  167 

small  masses  of  fibrin.  Frequently  the  whole  circumference 
of  the  vein  is  festooned  with  such  accumulations  of  cells  be- 
neath the  endothelium.  The  cells  of  the  latter  are  swollen, 
and  often  contain  pairs  of  the  minute  organisms.  In  capil- 
laries there  is  marked  thickening  of  the  endothelium  and 
filling  of  the  lumen  with  large  mononuclear  phagocytic  cells 
and  polymorphonuclear  leucocytes.  Surrounding  these  capil- 
laries are  zones  of  large  mononuclear  cells  (epithelioid  in  ap- 
pearance). In  these  large  mononuclear  cells  (endothelial  cells) 
there  are  numerous  minute  paired  organisms  and  smaller 
barely  visible  round  forms.  In  the  arteries  the  internal  elastic 
lamina  seems  to  form  the  center  of  the  lesions.  The  smallest 
lesions  consist  of  collections  of  endothelial  cells  overlying  a 
fragmented  and  basic  staining  portion  of  the  elastica,  while 
externally  (in  the  media)  there  may  appear  a  few  poly- 
morphonuclear leucocytes.  Large  lesions  show  deposits  of 
fibrin  internally  to  and  occasionally  externally  to  the  elastica. 
The  fibrin  in  the  lumen  of  the  vessels  is  coarsely  meshed  and 
contains  large  mononuclear  phagocytic  cells  and  polymorpho- 
nuclear leucocytes,  large  mononuclear  cells  and  a  rare  de- 
generated muscle  fiber,  shown  by  pycnotic  nucleus  and 
hyaline  cytoplasm.  In  arteries  showing  slight  lesions,  there 
are  festoon-like  projections  of  endothelial  cells  similar  to  those 
in  veins,  while  in  other  places  the  endothelium  is  thickened 
or  absent.  The  minute  paired  organisms  occur  in  greatest 
abundance  in  the  arteries,  packed  in  smooth  muscle  cells, 
some  of  which  show  hyaline  change,  in  large  mononuclear 
cells  (endothelial  cells)  in  the  media,  attached  to  the  intima, 
and  in  the  fibrin  meshes  of  the  thrombi.  They  also  occur 
apparently  free  beneath  the  elastica,  and  in  slightly  swollen 
endothelial  cells  in  regions  otherwise  normal.  The  packing 
of  the  organisms  in  smooth  muscle  cells  is  best  seen  in  longi- 
tudinal sections  of  the  cells  in  tangentially  cut  arteries. 
(2)  Six  different  blocks,  four  of  epididymis  and  two  of  ductus 
deferens,  with  pampiniform  plexus.  All  of  these  slides  show 
the  same  characteristic  extensive  lesions  of  blood  vessels, 
while  the  tubules  and  ducts  show  no  lesions.  In  one  slide 
of  the  pampiniform  plexus  an  artery  is  cut  longitudinally. 


1 68  WOLBACH. 

and  shows  the  entire  intima  elevated  and  enclosing  clusters  of 
large  mononuclear  phagocytic  cells  and  polymorphonuclear 
leucocytes.  Here  and  there  are  small  mural  fibrinous  thrombi, 
the  smallest  of  which  can  be  seen  to  have  taken  origin  upon- 
necrotic  phagocytic  mononuclear  cells.  In  the  necrotic  cells 
and  adjacent  to  them  there  are  always  many  of  the  minute 
paired  organisms. 

Skin    (Fig.    70) :     Blocks     from    axilla,     arms,    abdomen,, 
back,  buttocks,  thigh  and  leg  were  saved. 

Arm  and  axilla:  Arteries  and  veins  in  the  subcutaneous  fat 
and  in  the  deeper  layers  of  the  corium  show  lesions  of  the 
intima  with  and  without  mural  thrombi  of  fibrin,  such  as  have 
been  described  in  connection  with  the  epididymis  and  pampini- 
form plexus.  The  papillary  capillaries  and  the  vessels  of  the 
subpapillary  plexus  show  plugging  with  mononuclear  phago- 
cytic cells  (endothelial  cells),  and  polymorphonuclear  leuco- 
cytes, and  are  surrounded  by  zones  of  similar  cells  and  occa- 
sionally small  areas  of  hemorrhage.  Some  of  the  capillaries 
and  veins  contain  fibrin  as  well.  The  hemorrhages  are  most 
common  about  the  vessels  of  the  subpapillary  plexus;  they 
occur  also  about  small  veins  in  the  deeper  layers  of  the  corium 
and  in  the  subcutaneous  fat  lobules.  In  many  instances 
vessels  are  found  which  are  completely  filled  with  large  mono- 
nuclear cells,  some  containing  red  blood  corpuscles,  others 
polymorphonuclear  leucocytes,  while  some  are  not  phago- 
cytic. The  capillary  network  about  the  coil  glands  is  usually 
the  seat  of  similar  lesions.  Small  arteries  and  veins  with 
swollen  endothelium,  and  one  or  two  large  cells  (endothelial 
cells)  attached  to  one  point  where  there  is  a  trace  of  fibrin 
upon  the  intima,  are  common.  The  minute  parasites  are 
constantly  present  in  the  lesions  of  arteries  and  veins  in  smooth 
muscle  cells  and  in  endothelial  cells.  These  are  more  difificult 
to  find  in  the  plugged  capillaries  because  of  the  abundant 
granular  material  derived  from  degenerated  cells,  but  they 
can  be  invariably  found  within  endothelial  cells.  The  epi- 
dermis is  normal,  except  for  minute  areas  over  papillae  with 
plugged  capillaries  and  hemorrhage.     In  these  locations  the 


ROCKY   MOUNTAIN    SPOTTED    FEVER.  1 69 

epidermis  is  oedematous  and  infiltrated  with  polymorpho- 
nuclear leucocytes  and  occasionally  is  capped  with  an  adherent 
clump  of  keratinized  cells.  A  rare  nerve  trunk  shows  oedema 
and  infiltration  with  polymorphonuclear  leucocytes  and  mast 
cells;  the  latter  are  the  more  common.  The  subcutaneous 
fat  shows  a  few  areas  of  hemorrhage,  while  there  are  many 
places  which  are  infiltrated  with  large  mononuclear  cells  (en- 
dothelial cells),  phagocytic  for  red  blood  corpuscles  and  other 
cells.  The  coil  glands  where  the  capillaries  are  plugged  show 
marked  swelling  and  vacuolization  of  the  secretory  cells;  a 
few  are  infiltrated  with  polymorphonuclear  leucocytes.  The 
ducts  are  free  from  lesions. 

Abdomen:  The  lesions  are  similar  to  those  in  the  skin 
elsewhere  but  less  marked,  and  there  are  no  hemorrhages  into 
the  corium.     The  parasites  are  present  in  the  lesions. 

Thigh  and  leg:  The  character  and  extent  of  the  lesions  are 
similar  to  those  in  the  skin  from  the  arm.  The  parasites  are 
present  in  the  lesions. 

Buttocks:  The  character  of  the  lesions  is  similar  to  those 
elsewhere  in  the  skin,  but  there  is  more  extensive  involvement 
of  the  papillary  capillaries,  and  subpapillary  vessels,  and  small 
necrotic  foci  in  the  corium  occur  around  thrombosed  vessels 
of  small  caliber.  These  foci  are  filled  with  large  mononuclear 
phagocytic  cells  (endothelial  cells).  Small  areas  of  hemor- 
rhage are  likewise  more  frequent  in  the  papillae,  and  there  are 
occasionally  minute  necroses  of  the  overlying  epidermis.  The 
parasites  are  present  as  in  the  other  lesions. 

Scrotum:  Similar  lesions  of  blood  vessels  of  all  sizes  with 
presence  of  the  parasite  are  found  in  the  skin  and  dartos. 

Scharlach  R.  stain.  —  Heart:  There  are  large  areas  of 
fibers  showing  marked  fat  deposits  in  minute  droplets,  sufficient 
to  give  pink  color  to  the  fiber  with  low  power.  These  areas 
are  scattered  throughout  the  thickness  of  the  myocardium. 
There  is  moderate  amount  of  perinuclear  lipochrome.  Spleen : 
No  fat.  Liver:  Almost  devoid  of  fat,  A  narrow  zone  of 
fat  containing  liver  cells  is  found  about  the  portal  spaces- 


1 70  WOLBACH. 

The  fat  is  in  small  droplets.  Kidney:  An  occasional  con- 
voluted tubule  contains  a  few  small  droplets  of  fat  in  the 
epithelial  cells.  Adrenal:  The  middle  portion  of  the  fas- 
cicular zone  contains  considerable  lipoid  material.  The  glo- 
merular zone  contains  scattered  groups  of  cells  with  lipoid 
droplets. 

Case  IV.  —  This  case  was  that  of  a  young  male  adult,  a  laboratory 
technician  who  presumably  accidentally  introduced  the  virus  of  Rocky 
Mountain  spotted  fever  into  his  body  eight  days  before  the  onset  of  symp- 
toms, while  making  inoculations  from  guinea-pigs  to  guinea-pigs.  His 
symptoms  began  eight  days  before  death,  with  the  onset  of  a  sudden  fever, 
intermittent  headache  occurring  every  two  or  three  minutes,  with  remis- 
sions of  the  same  duration.  He  had  muscle  pains  in  both  thighs,  was 
constipated  and  feverish.  There  was  a  slight  cough  with  no  sputum. 
The  day  following,  seven  days  before  death,  he  had  a  chill  and  noticed  a 
rash  which  appeared  first  on  his  forearms. 

On  examination  six  days  before  death  there  was  an  "  erythematous 
maculo-papular  eruption  over  the  upper  extremities,  the  front  and  back 
of  the  chest  and  slightly  on  the  palms  of  the  hands  and  soles  of  the  feet. 
The  superficial  lymph  nodes  were  palpable  throughout,  but  not  greatly 
-enlarged."  There  was  an  ankle  clonus.  The  spleen  was  not  palpable. 
The  temperature  was  104°  F. 

Shortly  afterwards  a  slight  conjunctivitis  and  puffiness  of  the  face 
appeared.  The  eruption  extended  over  the  legs  and  feet  and  appeared  in 
the  mucous  membrane  of  the  mouth.  Two  days  before  death  the  erup- 
tion became  petechial  and  the  glandular  enlargement  more  marked. 
The  tongue  became  dry  and  brown.  The  pulse  and  respirations  became 
rapid  and  a  slight  rigidity  of  the  neck  appeared  the  day  before  death. 

Blood  cultures  during  life  were  negative.  The  diagnosis  of  Rocky 
Mountain  spotted  fever  was  confirmed  by  guinea-pig  inoculations. 

An  autopsy  was  made  two  hours  after  death.  Rigor  mortis 
was  slight  at  the  beginning  of  the  autopsy,  but  complete  when 
it  was  finished.  The  rash  remained  visible  after  death,  but 
the  erythematous  eruption  largely  disappeared  during  the 
autopsy.  Punctate  hemorrhages  into  the  skin  were  found 
most  marked  on  the  right  side,  on  the  abdomen,  chest,  thighs, 
shoulders  and  arms;  a  few  were  found  on  the  palmar  surface 
of  the  fingers  and  hands.  The  petechise  were  also  found  on 
the  fornices  of  the  conjunctivae,  mucosa  of  the  hard  palate 
and  lip  and  on  the  glans  penis.  The  skin  of  the  scrotum  was 
thick,  red  and  desquamating. 


ROCKY    MOUNTAIN'    SPOTTED    FEVER.  I7I 

The  abdominal  cavity  contained  about  two  hundred  cubic 
centimeters  of  liquid  blood,  which  came  from  a  rupture  at 
the  lower  pole  of  the  spleen.  The  cavities  of  the  chest  were 
normal.  The  heart  and  lungs  were  normal.  The  spleen 
weighed  seven  hundred  grams,  was  soft  in  consistency  and 
bluish-red  in  color.  "  At  its  lower  anterior  pole  there  is  a 
point  of  spontaneous  rupture  to  which  is  attached  a  blood  clot 
about  the  size  of  a  hen's  egg."  On  section  the  normal  struc- 
tures were  barely  visible,  and  the  pulp  was  dififluent. 

The  liver  weighed  nineteen  hundred  grams  and  was  not 
remarkable  in  appearance.  The  pancreas,  kidneys,  adrenal 
glands  and  gastro-intestinal  tract  were  normal  in  appearance. 
The  aorta  was  normal.  The  testes  were  not  remarkable  in 
appearance.  The  tunica  vaginalis  was  normal.  On  section 
both  testes  showed  a  marked  injection,  but  no  hemorrhages. 
The  thyroid  and  skeletal  muscles  were  normal.  The  bone 
marrow  (humerus)  was  red. 

Spotted  fever  Case  IV.  Microscopic  description.  Eosin- 
methylene-blue  and  Giemsa  stains.  (Fig.  44.)  Heart:  There 
are  three  sections,  including  one  through  the  base  of  a  large 
papillary  muscle.  All  show  very  slight  oedema,  but  otherwise 
normal.  The  pericardium  is  normal.  The  blood  vessels  are 
normal. 

Spleen:  Very  intensely  engorged,  with  small  hemorrhages 
and  fibrin  deposit  in  the  pulp.  The  Malpighian  bodies  are 
represented  in  most  instances  by  narrow  fringes  of  celis  around 
the  central  arteries.  They  show  no  evidence  of  proliferation. 
The  lymphoid  tissue  of  the  pulp  is  completely  replaced  by 
red  blood  corpuscles  and  polymorphonuclear  leucocytes;  the 
latter  occur  in  marked  excess,  and  in  many  places  they  form 
small  miliary-sized  collections.  They  are  also  grouped  in 
great  numbers  around  the  splenic  veins  and  sinuses.  Large 
mononuclear  phagocytic  cells  are  extremely  numerous  through- 
out the  spleen,  in  the  sinuses  and  in  the  reticular  tissue. 
They  contain  large  numbers  of  red  blood  corpuscles,  poly- 
morphonuclear leucocytes,  lymphoid  cells  and  nuclear  de- 
tritus. The  arteries  show  no  lesions.  The  connective  tissue 
structures  are  negative. 


172  WOLBACH. 

Liver:  There  is  moderate  injection.  The  sinusoids  con- 
tain many  mononuclear  cells  of  large  size,  free  and  attached 
to  the  sinusoid  walls.  Many  of  these  cells  are  phagocytic. 
They  are  occasionally  in  such  numbers  as  to  apparently 
occlude  the  sinusoids.  Scattered  throughout  the  liver  are 
minute  necroses  consisting  of  from  one  to  several  liver  cells, 
which  have  undergone  a  granular  hyaline  degeneration  and 
are  invaded  by  polymorphonuclear  leucocytes.  These  necro- 
ses are  scattered,  without  special  reference  to  any  one  zone 
in  the  lobules.  There  is  very  moderate  fat  vacuolation,  most 
pronounced  at  the  periphery  of  the  lobules.  The  bile  ducts 
are  normal.  The  bile  capillaries  show  distinctly,  by  virtue 
of  their  cuticular  borders;  none  contain  inspissated  bile. 
The  blood  vessels  of  the  portal  spaces  show  no  lesions,  except 
that  small  veins  and  capillaries  are  filled  with  large  mono- 
nuclear cells. 

Pancreas:     Normal.     Blood  vessels  of  pancreas  normal. 

Kidneys:  The  glomeruli  show  in  many  instances  an  in- 
crease in  nuclei,  which  is  due  to  accumulation  of  large  mono- 
nuclear cells  (endothelial  cells)  in  the  capillaries,  and  to  an 
occasional  migrating  polymorphonuclear  leucocyte.  A  few 
glomeruli  show  a  small  amount  of  granular  material  between 
the  capsule  and  the  capillary  tufts.  The  majority  of  capil- 
laries in  most  glomeruli  contain  red  blood  corpuscles.  Other- 
wise the  kidney,  including  blood  vessels,  is  normal. 

Intestines:  There  are  two  sections  of  the  ileum;  both  are 
normal.     Blood  vessels  are  normal. 

Adrenal  glands:     Normal. 

Blood  vessels  normal. 

Thyroid  gland:     Normal. 

Blood  vessels  normal. 

Prostate  gland:     Gland  and  blood  vessels  normal. 

Muscle  (source?):  An  occasional  fiber  shows  typical  Zen- 
ker's degeneration,  without  cellular  reaction.  Such  fibers  are 
swollen,  have  lost  their  striation,  and  have  a  homogeneous 
waxy  appearance,  except  where  they  have  separated  into 
irregular  globular  masses  of  hyaline  material.  In  one  of  two 
sections  examined,  a  medium-sized  artery  is  partially  occluded 


ROCKY   MOUNTAIN    SPOTTED    FEVER.  1 73 

by  a  fibrinous  thrombus.  The  lumen  contains  numerous 
large  mononuclear  cells,  and  some  of  them  are  phagocytic 
(endothelial  cells).  Some  of  these  cells  are  attached  to  the 
wall  of  the  artery.  The  media  is  infiltrated  with  polymorpho- 
nuclear leucocytes,  and  surrounding  the  artery  are  a  few  large 
mononuclear  cells  (endothelial  cells).  In  the  intima  and  in 
longitudinal  smooth  muscle  fibers  of  this  artery  there  are 
numerous  minute  paired  microorganisms  characteristic  of 
Rocky  Mountain  spotted  fever.  Other  smaller  blood  vessels 
show  no  lesions. 

Lymph  node:  Probably  bronchial,  because  of  carbon  pig- 
ment. The  sinuses  are  distended  with  blood,  and  contain 
also  large  numbers  of  large  mononuclear  cells,  many  of  which 
are  phagocytic  and  contain  red  blood  corpuscles  and  lymphoid 
cells.  The  secondary  follicles  are  small,  but  contain  occasional 
mitotic  figures. 

Aorta:     There  are  no  acute  lesions. 

Testes  and  epididymis:  The  seminiferous  tubules  are  nor- 
mal, and  show  normal  spermatogenesis.  In  a  few  places  in 
the  interstitial  tissue  surrounding  blood  vessels  occluded  by 
endothelial  cells  there  are  collections  of  similar  cells,  many 
of  which  are  phagocytic,  and  polymorphonuclear  leucocytes. 
In  a  few  locations  there  are  minute  collections  of  red  blood 
cells,  some  of  which  have  been  taken  up  by  mononuclear 
phagocytes.  The  larger  blood  vessels  in  the  substance  of 
the  testes  contain  large  numbers  of  endothelial  cells.  A  few 
show  masses  of  endothelial  cells  attached  to  the  intima, 
particularly  in  the  veins.  In  the  tunica  there  are  numerous 
arteries  and  veins  which  show  fibrinous  mural  thrombi.  Such 
vessels  contain  large  collections  of  endothelial  cells,  free  and 
attached  to  the  wall.  In  one  instance  there  is  an  artery  with 
the  whole  media  infiltrated  with  fibrin  and  migrating  cells 
with  a  perivascular  collection  of  amoeboid  mononuclear  (en- 
dothelial) cells  and  polymorphonuclear  cells.  In  the  vessel 
walls  showing  these  lesions,  both  in  endothelium  and  in 
smooth  muscle  cells,  are  great  numbers  of  the  minute  paired 
microorganisms,  such  as  have  been  described  in  the  previous 
cases.     Sections  of  the  epididymis  and  pampiniform  plexus 


174  WOLBACH. 

show  many  arteries  and  veins  with  similar  lesions  containing 
similar  minute  microorganisms.  The  tubules  of  the  epididy- 
mis are  normal. 

Skin  (Fig.  44) :  Sections  of  the  skin  and  subcutaneous 
tissues  from  several  different  sources,  including  the  scrotum, 
all  show  very  marked  lesions  of  blood  vessels  of  all  sizes, 
most  striking,  however,  in  arteries  and  veins  of  large  size 
in  the  subcutaneous  tissue  and  lower  layers  of  the  corium. 
These  vessels  contain  fibrinous  mural  thrombi  and  large 
numbers  of  endothelial  cells,  free  and  attached  to  the  vessel 
wall.  There  are  many  veins  of  intermediate  size,  which  are 
completely  filled  with  endothelial  cells.  The  smallest  lesions 
in  arteries  consist  of  endothelial  cells  attached  to  the  intima, 
frequently  accompanied  by  migrating  leucocytes  in  the  media. 
The  internal  elastic  lamina  is  usually  fragmented  at  the  site 
of  these  lesions.  The  minute  parasite  is  present  in  large 
numbers  in  endothelial  cells,  free  and  attached,  and  in  smooth 
muscle  cells  in  the  media.  There  are  many  striking  examples 
in  these  sections  of  smooth  muscle  cells  filled  with  organisms. 
(Fig.  44.)  With  the  highest  powers  the  lanceolate  shape 
and  a  surrounding  clear  zone  or  halo  are  easily  seen.  In  many 
sections  of  the  skin  there  are  small  veins  filled  with  endothelial 
cells  and  polymorphonuclear  leucocytes,  whose  walls  are  in- 
filtrated with  red  blood  corpuscles  and  fibrin.  Surrounding 
such  veins  are  small  areas  of  hemorrhage,  in  which  are  many 
mononuclear  phagocytic  cells,  containing  red  blood  cells. 
Lesions  of  the  latter  sort  are  common  in  the  vicinity  of  coil 
glands,  which  show  marked  degenerative  changes.  The 
epithelial  cells  are  swollen,  vacuolated,  and  often  are  ^des- 
quamated and  have  pycnotic  nuclei.  Occasionally  the  re- 
mains  of  coil  glands  are  encountered  heavily  infiltrated  with 
polymorphonuclear  leucocytes.  The  capillaries  of  the  papillae 
show  lesions  similar  to  those  found  near  the  coil  glands,  but  to 
a  less  marked  degree,  and  it  is  rare  to  find  extravasation  of 
blood  in  this  region.  Nerves  that  have  become  incorporated 
in  the  zones  of  infiltration  surrounding  blood  vessels  show 
occasional  migrating  mononuclear  cells  and  mast  cells  between 


ROCKY   MOUNTAIN    SPOTTED   FEVER.  1 75 

the  nerve  fibers.  Rarely  there  is  a  polymorphonuclear  leuco- 
cyte within  a  nerve  sheath.  The  epidermis  in  all  locations 
shows  practically  no  reaction.  That  of  the  scrotum  shows 
slight  thickening  in  small  areas,  probably  due  to  oedema  and 
proliferation. 

Case  V.  ^ — I  am  indebted  to  W.  T.  Thornton,  M.D.,  of 
Missoula,  Mont.,  for  the  notes  and  material  of  this  case. 
The  post-mortem  was  done  by  Dr.  Thornton  and  the  tissues 
preserved  in  accordance  with  my  directions.  No  gross  patho- 
logical conditions  are  recorded:  a  complete  set  of  tissues  was 
sent  to  me,  including  skin  from  the  arms,  trunk,  thighs,  legs, 
ankles  and  scrotum,  so  that  the  microscopical  findings  are 
of  great  value. 

The  case  was  that  of  a  male  adolescent  who  had  been  repeatedly  bitten 
by  ticks  during  the  spring,  so  that  the  period  of  incubation  was  uncertain. 
The  onset  was  gradual;  no  chill  was  noted  and  it  was  not  until  the  rash 
appeared  that  the  boy  was  regarded  as  sick.  He  was  seen  by  Dr.  Thorn- 
ton on  the  fourth  day  of  illness,  when  his  temperature  was  104°  F.,  his 
pulse  120  and  his  body  covered  with  a  rash.  He  died  on  the  eleventh 
day  after  a  typical  severe  course  of  the  disease,  with  "high  temperature 
and  delirium."  There  was  no  hyperjesthesia.  Muscular  rigidity  of  the 
extremities  began  on  the  fifth  day,  icterus  was  present  on  the  sixth  day, 
and  became  very  marked  before  death. 

The  autopsy  was  done  two  hours  after  death.  The  case 
was  regarded  by  Dr.  Thornton,  who  has  had  considerable 
experience  with  the  disease,  as  typical,  and  the  microscopical 
findings  are  typical  and  confirmatory  of  the  previous  cases 
in  regard  to  the  characteristic  histology  and  localization  of 
the  vascular  lesions  and  the  presence  of  the  parasite. 

Spotted  fever  Case  V.  Microscopic  description.  Eosin- 
methylene-blue  and  Giemsa  stains.  Heart:  There  are  two 
sections  of  the  left  ventricle  wall  and  one  of  the  right  ventricle 
wall.  All  show  in  the  inner  half  of  the  myocardium  and  par- 
ticularly in  the  muscle  columns  very  rare  minute  lesions  con- 
sisting of  collections  of  mononuclear  cells  in  and  around 
capillaries.  These  cells  are  mostly  amoeboid  in  type,  and  a 
few  are  phagocytic  (endothelial  leucocytes).  There  are  also 
a  few  polymorphonuclear  leucocytes,  lymphoid  and  plasma 


176  WOLBACH. 

cells  and  a  very  rare  mast  cell.  In  a  few  instances  polymor- 
phonuclear leucocytes  are  invading  muscle  fibers.  The  myo- 
cardium as  a  whole  appears  normal.  The  larger  vessels, 
arteries  and  veins  show  no  lesions.  In  the  pericardium  of 
the  right  ventricle  there  are  several  areas  of  infiltration  with 
cells  of  the  above  type,  and  small  arteries  and  veins  are  found 
containing  many  large  mononuclear  cells  (endothelial  cells), 
which  in  some  instances  are  still  attached  to  the  vessel  wall. 
No  parasites  can  be  found. 

Lung:  There  are  three  sections.  One  shows  large  patches 
of  bronchopneumonia.  The  exudate  consists  almost  wholly 
of  polymorphonuclear  leucocytes  and  fills  alveoli  and  bronchi- 
oles. There  is  no  fibrin.  There  are  numerous  large  mono- 
nuclear cells,  not  phagocytic  (desquamated  epithelium),  and 
a  rare  phagocytic  mononuclear  cell.  The  capillaries  in  the 
alveolar  walls  are  congested  and  contain  many  migrating 
polymorphonuclear  leucocytes  and  amoeboid  mononuclear 
cells.  In  the  alveoli  the  leucocytes  contain  many  micrococci, 
morphologically  identical  with  pneumococcus.  The  pleural 
surfaces  are  normal.  The  other  two  sections  show  no  exudate. 
The  capillaries  in  the  alveolar  wall  contain  a  large  number  of 
mononuclear  cells,  a  rare  one  of  which  is  phagocytic  (endo- 
thelial leucocyte).  In  a  few  locations  there  are  collections 
of  polymorphonuclear  leucocytes  in  the  alveolar  walls.  The 
pleura  is  normal. 

Spleen:  Intensely  injected.  The  Malpighian  bodies  are 
small,  irregular  in  size  and  contain  very  few  mitotic  lympho- 
cytes. The  pulp  is  nearly  completely  devoid  of  lymphocytes 
and  the  reticular  tissue  contains  chiefly  red  blood  cells,  numer- 
ous polymorphonuclear  leucocytes,  and  large  mononuclear 
phagocytic  cells  enclosing  red  blood  cells  and  polymorphonu- 
clear leucocytes.  The  sinuses  are  filled  with  blood  and  contain 
many  large  mononuclear  phagocytic  cells  distended  with  red 
blood  cells,  though  some  contain  polymorphonuclear  leuco- 
cytes and  lymphoid  cells.  There  are  numerous  migrating 
polymorphonuclear  leucocytes  in  the  sinus  walls.  The  arteries 
and  veins  show  no  lesions.  The  connective  tissue  structures 
are  normal. 


ROCKY    MOUNTAIN    SPOTTED   FEVER.  1 77 

Liver:  There  is  moderate  injection.  The  striking  feature 
of  the  organ  is  the  presence  of  many  mononuclear  phagocytic 
cells,  free  in  the  sinusoids,  or  attached  to  the  sinusoid  wall, 
and  containing  chiefly  red  blood  corpuscles,  but  also  occasional 
polymorphonuclear  leucocytes.  There  are  no  necroses  of  any 
size.  A  rare  liver  cell  shows  hyaline  change  and  invasion  by 
polymorphonuclear  leucocytes.  The  bile  ducts  are  normal 
and  the  bile  capillaries  are  not  distended.  In  the  portal 
spaces  occasional  arteries  and  veins  show  "slight  lesions  in  the 
form  of  endothelial  cell  collections  on  the  intima,  and  presence 
of  migrating  leucocytes  in  the  media.  Several  arteries  of  small 
size  show  numerous  minute  paired  microorganisms,  like  those 
described  in  the  preceding  case  in  smooth  muscle  cells  and  in 
endothelial  cells.  There  are  no  thromboses,  but  the  con- 
nective tissue  of  the  portal  spaces  containing  these  vessels 
with  lesions  is  infiltrated  with  mononuclear  amoeboid  cells 
(endothelial  leucocytes)  and  polymorphonuclear  leucocytes. 
Capillaries  and  lymphatics  are  frequently  filled  with  endo- 
thelial cells,  and  a  rare  capillary  contains  in  the  lining  endo- 
thelium a  few  of  the  minute  parasites. 

Kidney:  Normal,  except  for  an  occasional  large  mono- 
nuclear cell  in  the  glomerular  capillaries.  The  blood  vessels 
of  all  sizes  are  normal. 

Testis  and  epididymis:  Many  seminiferous  tubules  show 
no  signs  of  activity,  and  the  lumina  contain  cells  with  pyc- 
notic  nuclei;  on  the  ether  hand,  occasional  tubules  show 
many  mitoses,  but  rarely  contain  spermatozoa.  A  very  rare 
tubule  shows  complete  loss  of  spermatogenic  cells.  The  inter- 
stitial tissue  is  slightly  oedematous,  and  there  are  many  small 
areas  of  large  mononuclear  cells  grouped  about  small  blood 
vessels,  which  are  filled  with  similar  cells  (endothelial  cells). 
There  are  a  few  small  hemorrhages  into  the  interstitial  tissue 
and  these  areas  contain  phagocytic  cells  filled  with  red  blood 
corpuscles.  Small  arteries  and  veins  show  marked  thickening 
of  the  lining  endothelium,  and  in  the  cells  of  the  latter  are 
occasional  pairs  of  the  minute  paired  microorganisms.  A 
few  arteries  and  veins  of  the  tunica  albuginea  and  of  the 
pampiniform  plexus  show  fibrinous  mural  thrombi  overlying 


1 78  WOLBACH. 

lesions  of  the  intima,  which  are  characterized  by  clusters  of 
endothelial  cells  and  occasional  polymorphonuclear  leucocytes. 
The  media  always  contains  a  few  migrating  leucocytes,  and 
the  smooth  muscle  fibers  show  vacuolization  and  rarely  actual 
necrosis.  The  small  microorganisms  are  present  in  the  endo- 
thelial cells  and  smooth  muscle  fibers  in  small  numbers.  Small 
arteries  and  veins  and  capillaries  contain  many  mononuclear 
cells,  often  phagocytic  and  containing  red  blood  corpuscles. 

Stomach:     Normal.     The  blood  vessels  show  no  lesions. 

Intestines:  Sections  of  the  jejunum  and  ileum  are  normal. 
The  blood  vessels  show  no  lesions. 

Skin:  Sections  of  the  skin  and  subcutaneous  fat  from  the 
arms,  legs,  trunk,  ankles  and  scrotum  all  show  similar  lesions 
of  the  blood  vessels.  The  larger  arteries  and  veins  show 
occasional  small  lesions  in  the  form  of  endothelial  cell  pro- 
liferation of  the  intima  and  migrating  leucocytes  in  the  media. 
These  lesions  are  occasionally  the  site  of  small  fibrinous  mural 
thrombi.  Small  vessels  are  frequently  filled  with  mononuclear 
cells,  some  of  which  are  phagocytic.  The  most  marked 
changes  are  in  the  capillaries  of  the  corium,  about  coil  glands 
and  in  the  papillae;  in  these  locations  the  capillaries  are  filled 
with  mononuclear  cells,  and  are  surrounded  by  groups  of 
amoeboid  and  phagocytic  cells  (endothelial  cells),  with  occa- 
sional polymorphonuclear  leucocytes,  mast  cells  and  lymphoid 
cells.  In  many  instances  the  capillary  wall  is  difificult  to 
identify  because  of  the  packing  of  cells.  In  the  skin  of  the 
scrotum  there  is  intense  injection  of  the  blood  vessels,  and 
rarely  a  small  hemorrhagic  zone  occurs  about  capillaries. 
The  coil  glands  in  general  show  degenerative  changes,  vacuo- 
lization, pycnotic  nuclei  and  even  complete  disintegration, 
with  infiltration  of  polymorphonuclear  leucocytes.  In  sec- 
tions of  the  skin  from  all  of  the  above  locations,  the  minute 
paired  microorganisms  occur  in  the  vessel  walls,  in  endo- 
thelium and  in  smooth  muscle;  occasionally  in  large  numbers 
in  smooth  muscle  cells,  in  arteries  and  veins  showing  only 
slight  proliferation  of  the  endothelium. 

A  few  nerves  in  relation  to  vessels  with  perivascular  reaction 
show  a  rare  amoeboid  wandering  cell,  or  mast  cells  between 
the  nerve  fibers. 


ROCKY    MOUNTAIN    SPOTTED    FEVER.  I79 

Voluntary  muscle:  A  fragment  of  muscle  from  the  arm 
shows  vascular  lesions  like  those  of  the  skin  and  subcutaneous 
tissues. 


XVIII.       SUMMARY. 

Ricketts  and  his  associates  were  the  first  to  show  the 
hereditary  transmission  of  the  virus  in  ticks.  I  have  been 
able  to  verif\^  the  presence  of  the  virus  in  the  eggs  of  ticks, 
and  to  demonstrate  the  parasite  morphologically  in  ova  and 
in  spermatozoa  from  ticks.  The  susceptibility  of  the  small 
mammals  of  the  Rocky  Mountain  states  and  the  finding  of 
immune  animals  have  been  shown  by  Ricketts  and  Mc- 
Clintic.  It  seems  reasonable  to  suppose  that  alternation 
between  mammals  and  tick  occurs  frequently.  On  the  other 
hand,  it  seems  probable  that  the  virus  may  be  maintained 
in  many  generations  of  ticks  without  introduction  from  a 
mammalian  source,  but  that  this  may  last  indefinitely  cannot 
be  assumed.  J.  L.  Todd  has  found  that  the  spirochsete  of 
African  relapsing  fever  eventually  disappears  from  Onitho- 
dorus.  (Personal  communication.)  The  existence  of  local 
foci  of  infection  would  indicate  that  hereditary  transmission 
of  the  virus  in  ticks  is  an  important  factor  in  maintaining  the 
virus  in  nature.  The  tick  does  not  travel  great  distances  except 
when  attached.  The  range  of  the  small  mammals  on  which 
the  larval  or  nymph  stage  feed  is  restricted,  and  therefore  the 
carrying  of  infected  ticks  from  locality  to  locality,  can  only 
be  accomplished  by  the  larger  animals.  As  the  adults  engorge 
in  the  early  spring  months  on  range  animals,  this  probably 
does  not  play  a  very  important  part  in  the  dissemination  of  the 
ticks.  Engorged  females,  on  dropping,  seek  cover,  and  de- 
posit their  eggs  wherever  chance  has  placed  them.  Engorged 
females  dropping  from  cattle  in  transport  must  rarely  find 
conditions  suitable  for  the  hatching  and  rearing  of  the  larvse. 

These  factors  must  tend  to  retard  the  extension  of  the 
areas  occupied  by  infected  ticks.  The  sudden  appearance 
of  the  disease  in  eastern  Montana  in  1915  can  best  be -explained 
by  the  introduction  of  infected  ticks  upon  transported  animals. 


l8o  WOLBACH. 

The  movements  of  animals  with  the  disease  could  hardly 
account  for  such  a  wide  extension.  Human  cases  may  be 
disregarded  as  a  source  of  the  virus,  because  of  the  relatively 
small  number  of  individuals  acting  as  hosts,  and  because 
patients  with  the  disease  are  not  accessible  to  ticks,  while 
ticks  attached  to  their  persons  are  almost  invariably  destroyed. 

Mammalian  "  carriers  "  of  the  disease  have  not  been  dis- 
covered. In  all  experimental  animals  the  blood  ceases  to 
be  infective  after  the  subsidence  of  fever.  It  is,  however, 
permissible  on  theoretical  grounds  to  consider  the  possibility 
of  the  disease  existing  in  a  chronic  form  in  some  of  the  wild 
mammals  which  are  hosts  to  the  tick. 

The  question  of  the  consistent  difference  in  virulence  of  the 
disease  in  man  in  different  districts  is  impossible  of  explana- 
tion, and  its  study  requires  extensive  investigation  into  the 
duration  of  infectivity  and  character  of  the  disease  in  all 
animals  acting  as  tick  hosts.  Rapidly  repeated  passages  of 
the  virus  during  a  long  period  in  a  single  species  of  animal 
peculiar  to,  or  particularly  abundant  in,  a  given  locality, 
would,  conceivably,  modify  the  virulence  for  man.  For  this 
reason  a  careful  study  of  the  disease  in  rabbits  in  relation  to 
the  lower  mortality  of  the  disease  in  man  in  eastern  Montana, 
as  compared  with  the  mortality  in  western  Montana,  is 
highly  desirable.  Parker^^-  ^^  has  shown  that  the  rabbit  acts 
as  host  to  all  stages  of  the  tick,  a  fact  which  proves  the  pos- 
sibility of  more  numerous  passages  of  the  virus  through  this 
animal. 

The  susceptibility  of  the  larger  animals,  horses,  cattle  and 
sheep,  to  the  disease,  has  received  but  scant  attention,  and 
requires  investigation.  The  finding  of  infective  ticks  upon 
the  mountain  goat  suggests  another  much  needed  line  of 
research.  The  possibilities  of  an  immune  therapy  necessarily 
lie  in  the  discovery  of  a  large-sized  susceptible  animal. 

Rocky  Mountain  spotted  fever  as  a  disease  assumes  new 
interest  and  importance  now  that  its  nature  is  known.  The 
remarkable  specificity  of  the  parasite  for  the  peripheral  blood 
vessels  in  all  experimental  animals  and  in  man  is  of  significance 
in  relation  to  the  manner  of  transmission. 


ROCKY    MOUNTAIN    SPOTTED    FEVER.  l8l 

The  lesions  of  the  blood  vessels  are  due  to  the  presence  of 
the  parasite  and  constitute  the  distinctive  pathology  of  the 
disease,  and  warrant  the  definition  — "  An  acute  specific 
infectious  endangiitis,  chiefly  of  the  peripheral  blood  ves- 
sels .  .  .," — which  I  have  given.  The  character  and  evolu- 
tion of  the  rash  with  the  cutaneous  sequelae  (necrosis  or 
gangrene)  are  explained  by  the  blood  vessel  lesions.  The 
hyperesthesia  and  probably  the  restlessness  of  the  patients 
are  explained  by  the  secondary  involvement  of  nerves  in  the 
inflammatory  reaction  surrounding  blood  vessels  with  lesions. 

The  lesions  are  at  first  essentially  proliferative  (endo- 
thelium), followed  by  necrosis  of  small  groups  of  cells,  and 
the  chief  cellular  reaction,  both  locally  in  response  to  the 
presence  of  the  parasite,  and  in  general,  presumably  in  response 
to  toxins,  is  endothelial.  The  respiratory  symptoms  may 
be  due  in  part  to  a  central  action  of  toxins,  but  it  is  also 
reasonable  to  ascribe  some  effect  to  the  accumulation  of  en- 
dothelial cells  in  the  pulmonary  capillaries. 

The  icterus  is  due  to  red  blood  corpuscle  destruction,  and 
as  no  evidence  of  an  intracorpuscular  stage  of  the  parasite 
can  be  obtained,  is  probably  of  toxic  origin.  Fused  masses 
of  red  corpuscles  in  the  spleen  are  probably  a  stage  preliminary 
to  their  destruction,  an  assumption  which  is  further  supported 
by  the  accumulation  of  hemosiderin  in  endothelial  cells.  Evi- 
dence of  bile  stasis  in  the  liver  is  completely  lacking  in  all 
varieties  of  material  studied. 

There  are  two  diseases  which  clinically  have  a  strong  re- 
semblance to  Rocky  Mountain  spotted  fever,  and  which  will 
probably  eventually  be  classified  in  a  group,  the  chief  char- 
acteristics of  which  are  included  in  my  definition  of  Rocky 
Mountain  spotted  fever.  These  diseases  are  typhus  fever 
and  Tsutsugamushi  disease,  or  Japanese  river  fever  or  flood 
fever;  a  brief  comparison  of  each  with  Rocky  Mountain 
spotted  fever  follows. 

Typhus  fever  and  Rocky  Mountain  spotted  fever.  —  Typhus 
fever,  of  all  diseases,  is  most  like  Rocky  Mountain  spotted 
fever,  and  if  the  two  should,  exist  at  the  same  time  in  the  same 


1 82  WOLBACH. 

community  a  differential  diagnosis  without  animal  inoculation 
would  be  impossible.  The  course  of  the  two  diseases  and  the 
characteristics  of  the  rash  in  each  are  almost  identical.  Like 
the  virus  of  Rocky  Mountain  spotted  fever,  that  of  typhus 
is  not  filterable,  and  Nicolle  and  Blaizot'^^  find  indications 
of  the  same  susceptibility  to  physical  agents,  for  they  find 
that  the  virus  of  typhus  will  survive  but  six  days  on  ice  and 
but  two  days  at  37°  C. 

The  pathological  anatomy  of  typhus  is  not  distinctive. 
The.  spleen  is  not  uniformly  enlarged  as  in  spotted  fever. 
The  histology  of  the  skin  lesions  has  been  described  recently 
by  a  number  of  authors,  and  resembles  in  many  respects  that 
of  spotted  fever. 

There  are  a  few  clinical  differences  which  may  be  mentioned 
here.  Typhus  fever  is  transmitted  by  the  body  louse.  The 
incubation  period  is  longer  than  in  the  case  of  Rocky  Mountain 
spotted  fever,  usually  about  twelve  days.  The  rash  makes 
its  appearance  on  the  chest  and  shoulders  and  extends  over 
the  trunk,  before  appearing  on  the  arms  and  legs,  in  almost 
the  reverse  order  of  the  rash  in  Rocky  Mountain  spotted  fever. 
In  typhus,  enlargement  of  the  spleen  is  absent  or  less  marked 
than  in  spotted  fever.  Icterus,  which  is  almost  constant  in 
spotted  fever,  is  absent  in  typhus. 

Defervescence  of  the  fever  in  typhus  takes  place  more 
quickly  and  is  usually  regarded  as  occurring  by  crisis. 

Secondary  infections  and  pneumonia  are  more  common 
after  typhus. 

In  recent  years  the  bacterium-like  bodies  in  lice  first 
described  by  Ricketts^^  and  Hegler  and  von  Prowazek,''^  and 
named  Rickettsia  prowazekii  by  da  Rocha-Lima,^^  have  re- 
ceived much  attention,  and  much  support  as  the  causative 
agent  of  typhus  fever,  by  da  Rocha-Lima,  Sergent,  Foley 
and  Vialatte,^^  Proescher,^^  Toepfer  and  Schuessler,^^ 
Toepfer,^^  Otto  and  Dietrich^^  and  others. 

However,  a  large  number  of  microorganisms  have  been 
described  as  the  causative  agent  of  typhus.  M.  Rabino- 
witsch,^^  in  19 13,  cultivated  a  minute  "  cocco-bacillus,"  which 


ROCKY   MOUNTAIX    SPOTTED    FEVER.  1 83 

is  now  regarded  by  some  as  identical  with  Rickettsia.  Ni- 
colle,  Blanc  and  ConseiF^  found  cocco-bacilli  in  five  per  cent 
of  lice  collected  from  districts  where  there  was  no  typhus. 

Brumpt^^  found  Rickettsia  bodies  in  a  large  per  cent  of 
lice  from  healthy  persons,  and  proved  that  these  lice  were 
not  capable  of  transmitting  typhus  fever  by  allowing  fifty 
of  them  to  feed  upon  himself  on  two  or  three  occasions. 
Other  workers  have  found  Rickettsia  in  non-infective  lice,  and 
recently  Arkwright,  Bacot  and  Duncan^"  have  described 
Rickettsia  in  lice  fed  upon  trench  fever  patients. 

The  etiological  significance  of  Rickettsia  bodies  in  lice  and 
in  the  blood  of  typhus  patients  is  not  yet  proved,  and  as 
described  by  Ricketts,  von  Prowazek  and  da  Rocha-Lima, 
they  have  a  significant  resemblance  to  the  parasite  of  Rocky 
Mountain  spotted  fever.  The  recent  finding  of  lesions  of  the 
endothelium  in  the  blood  vessels  of  the  skin  by  Fraenkel,'^^-  ''^ 
Aschofif,^"  Poindecker,^^  Bauer, ^^  von  Chiari^^  and  Jaffe^'^ 
in  man,  and  by  Neill^"  in  guinea-pigs,  makes  it  seem  probable 
that  the  pathology  of  typhus  is  very  similar  to  that  of  Rocky 
Mountain  spotted  fever,  and  therefore  that  the  etiological 
relationship  of  Rickettsia,  at  least  as  observed  in  the  blood  of 
patients,  deserves  serious  consideration.  The  demonstration 
of  the  organism  in  the  vascular  lesions  of  typhus  would  do 
much  to  settle  the  question. 

Rocky  Mountain  spotted  fever  and  Tsutsugamushi  disease, 
or  Japanese  flood  or  river  fever.  —  The  similarity  between 
these  two  diseases  has  long  excited  attention.  Ashburn  and 
Craig^  in  1908  published  a  comparative  study,  with  the  con- 
clusion that  they  were  not  identical,  though  presenting  many 
points  of  resemblance.  The  resemblances,  as  well  as  the 
differences  between  the  two,  are  made  accessible  for  a  more 
complete  comparison  by  the  recent  paper  of  Kitashima  and 
Miyajima.^^  Tsutsugamushi  disease  clinically  presents  a  very 
strong  resemblance  to  Rocky  Mountain  spotted  fever.  It  is 
transmitted  by  the  bite  of  the  larva  of  an  acarinen,  commonly 
called  the  akamushi  mite,  about  whose  scientific  name  there 
has  been  considerable  discussion.     The  acarinen  in  question 


184  WOLBACH. 

has  been  considered  to  be  a  trombidium,  and  was  named 
Trombidium  akamushi  by  Brumpt.  The  Hfe  cycle  has  re- 
cently been  studied  by  Miyajima  and  Okumura,^^  who  point 
out  differences  between  the  akamushi  mite  and  trombidium, 
and  its  similarity  to  another  genus  —  Leptus,  They  accord- 
ingly propose  the  name  Leptus  akamushi. 

The  virus  of  Tsutsugamushi  disease,  according  to  Kitashima 
and  Miyajima,  like  that  of  spotted  fever,  is  not  filterable,  and 
is  extremely  susceptible  to  chemical  and  physical  agents. 

Tsutsugamushi  disease,  like  Rocky  Mountain  spotted  fever, 
is  limited  to  certain  districts  infected  with  its  intermediate 
host,  Leptus  akamushi  {Trombidium  akamtishi),  namely  the 
provinces  of  Akita  and  Niigata  in  Japan.  A  similar  disease 
in  Java  is  transmitted  by  the  larval  stage  of  a  mite  whose 
habitat  is  in  districts  flooded  at  certain  seasons  of  the  year. 

The  mortality,  like  that  of  spotted  fever,  varies  in  different 
districts,  but  unlike  the  latter,  it  varies  from  season  to  season 
in  the  same  districts ;  and  ranges  from  fourteen  per  cent  to 
fifty-five  per  cent.  As  in  the  case  of  spotted  fever,  it  is  less 
fatal  in  the  young.  The  majority  of  fatal  cases  die  within 
twenty  days;  in  Kitashima's  and  Miyajima's  series  of  three 
hundred  out  of  three  hundred  sixty-eight  fatal  cases,  ninety- 
four  died  within  ten  days.  The  incidence  is  naturally  highest 
among  those  exposed  to  the  bites  of  the  mite,  and  hence  in 
land  laborers. 

The  incubation  period  is  seven  to  ten  days,  but  may  be  as 
long  as  twelve  to  fourteen  days.  The  prodromal  symptoms 
and  onset  are  similar  to  those  of  Rocky  Mountain  spotted 
fever.  The  fever  reaches  a  maximum  in  three  to  four  days, 
40°  to  41°  C,  and  is  of  the  continuous  type  and  lasts  one  to 
three  weeks,  falling  by  lysis.  The  rash  appears  on  the  fifth 
to  ninth  day  and  does  not  become  hemorrhagic  as  in  the  case 
of  spotted  fever,  it  usually  disappears  within  a  week.  The 
pulse  remains  slow  as  compared  with  Rocky  Mountain  spotted' 
fever,  90  to  100,  and  is  full  and  strong,  varying  in  proportion 
to  the  fever. 

In  favorable  cases  recovery  is  complete  by  the  fourth  to 
fifth  week.     Two  symptoms  occur  in  Tsutsugamushi  disease 


ROCKY    MOUNTAIN    SPOTTED    FEVER.  185 

which  are  absent  in  Rocky  Mountain  spotted  fever,  a  general 
painful  swelling  of  the  peripheral  lymph  nodes  and  necrosis 
of  the  skin  at  the  site  of  the  mite  bite. 

Nothing  distinctive  in  the  pathological  anatomy  has  been 
described.  The  spleen  becomes  enlarged.  The  white  blood 
count  is  at  first  below  normal  and  later  above  normal  for  a 
short  period. 

Monkeys  and  guinea-pigs  are  susceptible  to  experimental 
inoculation;  the  latter,  however,  do  not  give  a  characteristic 
reaction  as  does  the  monkey.  The  field  mouse,  Microtiis 
montehelli,  is  also  susceptible,  and  is  believed  to  be  the  impor- 
tant natural  mammalian  host  of  the  virus. 

The  analogies  between  Rocky  Mountain  spotted  fever  and 
Tsutsugamushi  disease  are  many.  The  chief  differences, 
besides  that  of  locality  and  nature  of  the  intermediate  host,  are 
in  the  milder  character  of  the  rash,  lymph  node  enlargement, 
and  necrosis  of  the  site  of  the  mite  bite  in  the  latter. 


A  summary  of  the  data  upon  which  the  conclusion  has  been 
reached  that  the  microorganism  described  is  the  causative 
agent  of  Rocky  Mountain  spotted  fever  includes  the  following 
facts. 

1.  The  constant  occurrence  of  a  microorganism  of  distinc- 
tive size  and  morphology  in  the  lesions  characteristic  of  the 
disease  in  man,  monkey,  rabbit  and  guinea-pig. 

2.  The  constant  presence  of  an  identical  microoorganism 
exhibiting  undoubted  evidences  of  developmental  phases  in 
ticks  of  proved  infectivity,  and  the  absence  of  similar  forms 
in  proved  non-infective  ticks. 

3.  The  ability  to  recognize  this  specific  microorganism  in 
the  tissues  and  eggs  of  infective  ticks  in  the  presence  of 
bacteria  occasionally  present  in  abundance  in  ticks  of  the 
species  concerned. 

The  failure  to  cultivate  this  parasite  is  balanced  by  the 
proof  furnished  of  its  multiplication  in  and  inseparability  from 
infective  ticks,  and  its  absence  in  non-infective  ticks.  The 
bacilli  seen  by  Ricketts  in  large  numbers  in  the  tissues  and 


1 86  WOLBACH. 

eggs  of  non-infective  as  well  as  infective  ticks  are  not  to 
be  confused  with  any  phase  of  the  spotted  fever  parasite. 
Ricketts  did  describe  one  form  of  this  parasite  which  he  found 
in  blood  films,  namely,  the  lanceolate  form. 

The  reasons  for  concluding  that  the  parasite  of  Rocky 
Mountain  spotted  fever  is  not  a  bacterium,  in  the  ordinary 
sense  of  the  term,  are: 

1.  Its  morphological  sequence  in  infected  nymphs,  and 
the  presence  of  only  one  morphological  type  in  the  blood  of 
mammals. 

2.  Its  staining  reactions  and  its  appearance  under  dark 
field  illumination. 

3.  Its  extreme  susceptibility  to  physical  and  chemical 
agents. 

4.  Its  specificity  for  the  peripheral  blood  vessels,  with  the 
production  of  an  identical  type  of  lesion  and  disease  course 
in  all  susceptible  mammals. 

Bacteria  which  are  the  causes  of  epidemics  often  show  a 
striking  specificity  for  certain  tissues,  for  example,  the  me- 
ningococcus in  epidemic  cerebrospinal  fever,  the  pneumococcus 
in  pneumonia,  and  the  typhoid  bacillus  in  typhoid  fever.  In 
each  of  these  diseases  a  preliminary  invasion  of  the  blood 
stream  has  been  proved,  yet  the  bacteria  thrive  best  and 
produce  their  deleterious  effects  in  certain  tissues  only.  These 
bacteria,  while  pathogenic  for  animals,  do  not  reproduce  the 
diseases  as  they  occur  in  man.  Meningitis,  it  is  true,  can  be 
produced  by  direct  inoculation  into  the  meninges  of  menin- 
gococcus cultures,  or  of  numerous  other  pathogenic  bacteria, 
while  it  is  impossible  to  reproduce  lobar  pneumonia  and  ty- 
phoid fever  in  animals  by  any  means.  The  viruses  of  rabies, 
poliomyelitis  and  vaccinia,  on  the  other  hand,  if  introduced 
into  susceptible  animals,  do  reproduce  the  diseases  which 
they  cause  in  man. 

Classification  with  the  protozoa  also  presents  difficulties, 
chief  of  which  is  the  lack  of  definite  morphological  proof, 
a  difficulty  largely  dependent  upon  the  minute  size  of  the 


ROCKY   MOUNTAIN    SPOTTED    FEVER.  187 

parasite.  Protozoa  are  for  the  most  part  highly  specialized 
in  their  host  requirements,  particularly  those  protozoa  which 
are  intracellular.  The  hemo-flagellates  exhibit  greatest  versa- 
tility in  this  respect,  but  not  comparable  with  that  of  the 
spotted  fever  parasite,  with  its  wide  range  of  mammalian 
hosts. 

Three  definite  morphological  types  of  the  spotted  fever 
parasite  can  be  recognized:  d)  An  extra-nuclear  bacillus-like 
form  without  chromatoid  granules,  relatively  large  and  only 
present  in  ticks  during  the  initial  multiplication  of  the  para- 
sites; (2)  a  relatively  small  rod-shaped  form  with  chroma- 
toid granules,  probably  the  same  form  seen  within  nuclei  in 
sections  of  ticks,  and  rarely  in  smooth  muscle  cells  in  the 
blood  vessels  of  mammals;  and  (3)  a  relatively  large  lanceolate 
paired  form  present  in  ticks  and  in  the  blood  and  lesions  in 
mammals.  This  lanceolate  form  is  characterized  by  its 
"  chromatoid  "  staining  reaction,  and  according  to  the  evidence 
at  hand,  is  the  form  in  which  the  virus  is  passed  between  the 
tick  and  mammalian  hosts.  The  other  two  forms  described 
are  multiplicative  stages,  and  can  only  be  demonstrated 
occasionally  and  with  difficulty  in  mammalian  hosts. 

The  name  Dermacentroxenus  rickettsi  is  proposed  for  this 
parasite. 

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54.  Ricketts,  H.  T.,  and  Gomez,  L.  Studies  on  immunity  in  Rocky 
Mountain  spotted  fever.     Journ.  Infect.  Dis.,  v,  221,  1908. 

55.  Ricketts,  H.  T.  A  microorganism  which  apparently  has  a  specific 
relationship  to  Rocky  Mountain  spotted  fever.  A  preliminary  report. 
Journ.  Am.  Med.  Ass.,  Hi,  379,  1909. 

56.  Ricketts,  H.  T.  Some  aspects  of  Rocky  Mountain  spotted  fever 
as  shown  by  recent  investigations.  The  Wesley  M.  Carpenter  lecture  of 
the  New  York  Academy  of  Medicine,  1909.  Med.  Record,  Ixxvi,  842,. 
1909. 


ROCKY   MOUNTAIN    SPOTTED    FEVER.  I9I 

57.  Robinson,  L.  E.,  and  Davidson,  J.  The  anatomy  of  Argas  persi- 
cus  (Oken,  1818).     Parasitology,  vl,  Nos.  i,  3  and  4,  1913-1914. 

58.  Rucker,  W.  C.  Rocky  Mountain  spotted  fever.  U.  S.  Pub. 
Health  Serv.,  Weekly  Reports,  xxvii.  No.  36,  1912. 

59.  Salmon,  D.  E.,  and  Stiles,  Ch.  Wardwell.  Cattle  ticks  (ixodoidea) 
of  the  United  States.  U.  S.  Dept.  of  Agriculture,  Bureau  of  AnimaJ 
Industry,  17th  Annual  Report  for  1900,  1902. 

60.  Samson,  Katharina.  Zur  anatomie  und  Biologic  von  Ixodes 
ricinus  L.     Zeitsch.  f.  Zool.,  xciii.  No.  2,  1909. 

61.  Spencer,  W.  O.  Mountain  or  spotted  fever  as  seen  in  Idaho  and 
eastern  Oregon.     Medical  Sentinel,  xv,  No.  11,  1907. 

62.  Stewart,  J.  L.,  and  Smith,  W.  F.  Clinical  phases  of  Rocky  Moun- 
tain spotted  fever.     Medical  Sentinel,  xvi,  December,  1908. 

63.  Stiles,  Ch.  Wardwell.  A  zoological  investigation  into  the  cause, 
transmission,  and  source  of  Rocky  Mountain  "  spotted  fever."  U.  S. 
Pub.  Health  and  Marine  Hosp.  Serv.,  Hyg.  Lab.  Bull.,  No.  26,  1905. 

64.  Stiles,  Ch.  Wardwell.  The  correct  name  of  the  Rocky  Mountain 
spotted  fever  tick.     Journ.  Am.  Med.  Ass.,  Iv,  No.  22,  1909,  1910. 

65.  Stiles,  Ch.  Wardwell.  The  taxonomic  value  of  the  microscopic 
structure  of  the  stigmal  plates  in  the  tick  genus  Dermacentor.  U.  S.  Pub. 
Health  and  Marine  Hosp.  Serv.,  Hyg.  Lab.  Bull.,  No.  62,  1910. 

66.  Tuttle,  T.  D.  Some  indications  for  state  control  of  Rocky  Moun- 
tain tick  fever.     Medical  Sentinel,  xvi,  December,  1908. 

67.  Wilson,  Louis  B.,  and  Chowning,  William  M,  The  so-called 
"  spotted  fever  "  of  the  Rocky  Mountains.  A  preliminary  report  to  the 
Montana  State  Board  of  Health.  Journ.  Am.  Med.  Ass.,  xxxix,  No.  3, 
1902. 

68.  Wilson,  Louis  B.,  and  Chowning,  William  M.  Studies  in  Pyro- 
plasmosis  hominis  ("  spotted  fever  "  or  "  tick  fever  ")  of  the  Rocky  Moun- 
tains.    Journ.  Infect.  Dis.,  1904,  i.  No.  i. 

69.  Wood,  W.  W.  Spotted  fever  as  reported  from  Idaho.  Report 
of  the  surgeon-general  of  the  army  to  the  Secretary  of  War,  1896. 


Other  References.  —  Typhus. 

70.  Aschoff,  L.  Ueber  anatomische  Befunde  bei  Fleckfieber.  Med. 
Klinik.,  xi.  No.  29,  1915. 

71.  Bauer,  E.  Zur  Anatomie  und  Histologic  des  Flecktyphus.  Miinch. 
Med.  Wochenschr.,  Ixiii,  No.  15,  1916. 

72.  Brumpt,  E.  Au  sujet  d'un  parasite  {Rickettsia  proivazeki)  des 
poux  I'homme  considere,  a  tort,  conime  I'agent  causal  du  typhus  exan- 
thematique.     Bull.  Soc.  Path.  Exotique,  xi.  No.  3,  1918. 

73.  von  Chiari,  R.  F.  Die  Veranderungen  der  Bindehaut  des  Auges 
bei  Fleckfieber.     Wien.  Klin.  Wochenschr.,  xxx.  No.  47,  19 17. 

74.  Fraenkel,  E.  Ueber  Fleckfieber  und  Roseola.  Miinch.  Med. 
Wochenschr.,  Ixi,  No.  2,  1914. 

75.  Fraenkel,  E.  Zur  Fleckfieberdiagnose.  Miinch.  Med.  Wochen- 
schr.,.Ixii,  No.  24,  1915. 


192  WOLBACH. 

76.  Hegler,  C,  and  von  Prowazek,  St.  Untersuchungen  iiber  Fleck- 
fieber  (Vorlaiifiger  Bericht).     Berlin.     Klin.  Wochenschr.,  1,  No.  3,  1913. 

77.  Jaffe,  R.  Zur  Pathologischen  Anatomic  des  Fleckfiebers.  II. 
Mikroskopische  Untersuchungen  mit  besondern  Beriicksichtigung  ganz 
frisches  und  ganz  alter  Falle.     Med.  Klinik.,  xiv,  No.  23,  1918. 

78.  NicoUe,  C,  Blanc,  G.,  and  Conseil,  E.  Quelques  points  de  I'etude 
■experimentale  du  typhus  exanthematique.  Compt.  Rend.  Acad.  Sci., 
clix,  No.  19,  1914. 

79.  Nicolle,  C,  and  Blaizot,  L.  Nouvelle  recherches  sur  le  typhus 
■exanthematique  (conservation  et  siege  du  virus).  Compt.  Rend.  Acad. 
Sci.,  clxi,  No.  21,  1915. 

80.  Neill,  M.  H.  Experimental  typhus  fever  in  guinea-pigs.  A 
description  of  a  scrotal  lesion  in  guinea-pigs  infected  with  Mexican  typhus. 
U.  S.  Pub.  Health  Serv.,  Weekly  Report,  xxxii,  No.  28,  1917. 

81.  Otto,  R.,  and  Dietrich.  Beitrage  zur  "  Rickettsein "  Frage. 
Deut.  Med.  Wochenschr.,  xliii,  No.  19,  1917. 

82.  Proescher,  Fr.  Zur  Etiologie  des  Fleckfiebers.  Berlin.  Klin. 
Wochenschr.,  Hi,  No.  31,  1915. 

83.  Poindecker,  Hans.  Zur  Diagnose  des  Fleckfiebers  in  Felde. 
Miinch.  Med.  Wochenschr.,  Ixiii,  No.  5,  1916. 

84.  Rabinowitsch,  Marcus.  Ueber  den  Flecktyphuserreger.  Miinch. 
Med.  Wochenschr.,  Ix,  No.  44,  1913. 

85.  Ricketts,  H.  T.  The  etiology'  of  the  typhus  fever  (Tabardillo) 
of  Mexico  City.     Journ.  Am.  Med.  Ass.,  liv,  1373,  1910. 

86.  da  Rocha-Lima,  H.  Zur  Aetiologie  des  Fleckfiebers.  Berlin. 
Klin.  Wochenschr.,  liii.  No.  21,  1916. 

87.  Sergent,  Edm.,  Foley,  H.,  and  Vialatte,  C.  Sur  des  formes 
microbiennes  abondantes  dans  le  corps  de  poux  infectes  par  le  typhus 
exanthematique  et  toujours  absentes  dans  le  poux  temoins  non-typh- 
iques.     Compt.  Rend.  Soc.  Biol.,  Ixxvii,  No.  21,  1914. 

88.  Toepfer,  H.,  and  Schuessler,  H.  Zur  Aetiologie  des  Fleckfiebers. 
Deut.  Med.  Wochenschr.,  xlii,  No.  38,  1916. 

89.  Toepfer,  H.  Der  Fleckfiebererreger  in  der  Laus.  Deut.  Med. 
Wochenschr.,  xlii,  No.  41,  1916. 


Other  References.  -—  Miscellaneous. 

90.  Arkwright,  J.  A.,  Bacot,  A.,  and  Duncan,  F.  Martin.  The  Asso- 
ciation of  rickettsia  with   trench   fever.     Journ.  Hyg.,  xviii,  No.  i,  1919. 

91.  Goodpasture,  E.  W.,  and  Burnett,  F.  L.  The  pathology  of  pneu- 
monia accompanying  influenza.  U.  S.  Naval  Medical  Bull.,  xiii.  No.  2, 
1919. 

92.  Kitashima,  T.,  and  Miyajima,  M.  Studien  uber  die  Tsutsuga- 
mushi-Krankheit.     Kitasato  Arch,  of  Exper.  Med.,  ii,  Nos.  2  and  3,  1918. 

93.  Miyajima,  M.,  and  Okomura,  T.  On  the  life  cycle  of  the  "  Aka- 
mushi."     Kitasato  Arch,  of  Exper.  Med.,  i.  No.  i,  1917. 

94.  Smith,  Theobald.  A  characteristic  localization  of  Bacillus  abortus 
in  the  bovine  fetal  membranes.     Journ.  Exper.  Med.,  xxix.  No.  5,  1919. 


ROCKY   MOUNTAIN    SPOTTED    FEVER.  I93 

95.  Tyzzer,  Ernest  Edward.  A  fatal  disease  of  the  Japanese  waltzing 
mouse,  caused  by  a  spore-bearing  bacillus  {Bacillus  piliformis  N.  Sp.). 
Journ.  Med.  Research,  xxxvii,  No.  2,  1917-1918. 

96.  Wolbach,  S.  B.  The  distribution  and  morphology  of  Spirocheta 
duttoni  and  SpirochcBta  kochi  in  experimentally  infected  ticks  (Omthodorus 
moubata).     Journ.  Med.  Research,  xxx.  No.  i,  1914. 

97.  Wolbach,  S.  B.,  Chapman,  W.  H.,  and  Stevens,  H.  W.  Concern- 
ing the  filterability  of  trypanosomes.  Journ.  Med.  Research,  xxxiii.  No.  i, 
1915- 


XX.     DESCRIPTION  OF  PLATES  I.  — XXI. 

Plate  I.,  Fig.  i.  — A  typical  ranch  or  farm  on  the  west  side  of  the 
Bitter  Root  Valley.  To  show  the  character  of  the  country,  and  unmelted 
■snow  in  the  month  of  May. 

Fig.  2.  —  Photograph  of  a  heavily  tick-infested  region.  Mouth  of  a 
■canyon,  west  side  of  Bitter  Root  Valley. 

Plate  II.,  Figs.  3  and  4.  —  Wire  gauze  cages  sewn  to  adhesive  plaster 
as  used  in  feeding  ticks. 

Fig.  5.  —  Cage  applied  to  abdomen  of  a  guinea-pig. 

Figs.  6  and  7.  —  Two  stages  in  the  necrosis  of  the  ear  of  a  rabbit  re- 
covering from  Rocky  Mountain  spotted  fever. 

Plate  III.,  Fig.  8.  —  Unfed  larva  of  Dermacentor  venustus,  8  diameters. 
Fig.  9.  —  Engorged  larva  of  Dermacentor  venustus,  8  diameters. 
Fig.  id.  —  Unfed  nymph  of  Dermacentor  venustus,  8  diameters. 

—  Engorged  females,  Dermacentor  venustus,  natural  size. 

—  Unfed  female,  Dermacentor  venustus,  8  diameters. 

—  Unfed  male,  Dermacentor  venustus,  8  diameters. 

—  Engorged  nymph  of  Dermacentor  venustus,  8  diameters. 

—  Engorged  female,  with  eggs,  Dermacentor  venustus,  natural 


Fig.  II 
Fig.  12 
Fig.  13 
Fig.  14 
Fig.  15 
size. 


Plate  IV.,  Fig.  16.  —  Male,  Dermacentor  venustus,  ventral  side. 
Fig.  17.  —  Female,  Dermacentor  venustus,  ventral  side. 

Plate  V.,  Figs.  18  and  19.  —  Dorsal  and  ventral  dissections  of  partially 
fed  females,  Dermacentor  venustus. 
Explanation  of  numbers  and  letters: 
I.     Salivary  glands. 


Genital  aperture. 
Brain. 
Vagina. 
Uterus. 


194  WOLBACH. 

6.  Oviduct. 

7.  Malpighian  tube. 

8.  Rectal  sac. 

9.  Anal  aperture. 

10.  Ovary. 

11.  Hind  gut  or  rectum. 

A.  Antero-lateral  division  of  intestines. 

B.  Anterior  diverticulum. 

C.  Lateral  diverticulum. 

D.  Posterior  diverticulum, 

E.  Internal  branch  of  posterior  diverticulum. 

F.  External  branch  of  posterior  diverticulum. 

G.  Mid-intestine. 

H.  External  branch  or  diverticulum  of  posterior  lateral  division 
of  intestine. 

I.  Internal  branch  or  diverticulum  of  posterior  lateral  division 
of  intestine. 


Plate  VI.,  Fig.  20.  —  Initial  form  of  the  parasite  of  Rocky  Mountain 
spotted  fever,  Tick  XLVIII.     Smear  of  intestinal  content,  2,000  diameters. 

Fig.  21.  —  Minute  rod  form  of  the  spotted  fever  parasite,  showing 
chromatoid  granules.  Tick  LXXIX.  Smear  of  intestinal  content,  2,000 
diameters. 

Fig.  22.  —  Smear  of  intestinal  content.  Tick  LXXXI.  Minute  form 
of  the  parasite  with  chromatoid  granules. 

Fig,  23.  —  Smear  preparation  from  eggs  of  a  tick  which  had  partly 
engorged  upon  a  horse  in  the  Bitter  Root  Valley.  Shows  the  bacilli  which 
are  common  in  the  eggs  and  tissues  of  Dermacentor  venustus,  and  probably 
the  cause  of  Ricketts's  confusion,  2,000  diameters. 

Fig.  24.  —  Drawings  from  thick  film  preparations  from  monkeys  and 
guinea-pigs,  showing  the  lanceolate  forms  of  the  Rocky  Mountain  spotted 
fever  parasite.     1,500  diameters. 

Fig.  25.  —  Schematic  enlargement  from  a  thick  film  preparation  of 
the  Rocky  Mountain  spotted  fever  parasite,  to  show  differential  staining. 

Fig.  26.  —  Lanceolate  forms  of  the  parasite  in  eggs  of  Tick  XXXI I. 
2,000  diameters. 

Fig.  27.  —  Section  of  Malpighian  tube  of  Tick  LXXXI.  Giemsa's 
stain.  Intra-nuclear  forms  of  the  parasite  in  a  greatly  distended  nucleus. 
1,500  diameters. 

Fig.  28.  —  Smear  preparation  of  salivary  gland  of  Tick  XI.  Shows 
lanceolate  and  minute  forms  of  the  parasite.     1,500  diameters. 

Fig.  29.  —  Smear  preparation  of  teased  tissues  from  skin  of  Guinea 
Pig  15,  Strain  I.  Shows  rod  and  lanceolate  forms  of  the  parasite.  1,500 
diameters. 

Plate  VII.,  Fig.  30.  —  Smear  preparation.  Tick  XXXIV.,  Malpighian 
tube,  showing  lanceolate  and  minute  rod  forms  with  chromatoid  granules. 
Photomicrograph  2,000  diameters. 


ROCKY    MOUNTAIN    SPOTTED    FEVER.  I95 

Fig.  31.  —  Section  of  nerve  trunk,  Tick  XXI.,  Giemsa's  stain,  showing 
parasites.     Photomicrograph  2,000  diameters. 

Fig.  32.  —  Same  as  Fig.  27.     Photomicrograph,  2,000  diameters. 

Fig.  33.  —  Smear  preparation.  Tick  XIII.,  salivary  gland,  minute  rod 
forms  with  chromatoid  granules.     Photomicrograph,  2,000  diameters. 

Fig.  34.  —  Smear  preparation.  Tick  XLVTII.,  intestinal  contents. 
Initial  form  of  parasite.     Photomicrograph,  2,000  diameters. 

Fig.  35.  —  Smear  preparation.  Tick  LXXXI.,  intestinal  contents. 
Minute  rod  form  with  chromatoid  granules.  Photomicrograph,  2,000 
diameters. 

Plate  VIII.,  Fig.  36.  —  Section  of  salivary  gland  acinus,  Type  i, 
Tick  XIII.,  Giemsa's  stain,  showing  the  parasites  in  gland  cells  and  in 
lumen  of  gland.      1,500  diameters. 

Fig.  37.  —  Section  of  intestine.  Tick  XI.,  Giemsa's  stain,  showing 
parasites  in  wall  of  intestine,  and  within  a  muscle  fiber.  1,500  diameters. 
Compare  with  photograph,  Fig.  43. 

Fig.  38.  —  Section  of  salivary  gland  acinus,  Type  2,  Tick  XIV.,  showing 
parasites.     1,500  diameters. 

Fig.  39.  —  Section  of  nerve  trunk,  Tick  XXI.,  1,000  diameters.  Com- 
pare with  photomicrograph.  Fig.  31*. 

Fig.  40.  —  Section  of  leg  muscle.  Tick  XIV.,  showing  parasites.  1,500 
diameters. 

Plate  IX.,  Fig.  41.  —  Section  of  salivary  gland  duct.  Tick  XIV., 
Giemsa's  stain,  showing  minute  forms  of  parasite.  Photomicrograph, 
2,000  diameters. 

Fig.  42.  Section  of  Malpighian  tube.  Tick  XIV.,  showing  a  nucleus 
distended  with  the  parasites.     Photomicrograph,  2,000  diameters. 

Fig.  43.  —  Same  as  Fig.  37.  Photomicrograph  at  2,000  diameters  of 
muscle  fiber  filled  with  the  minute  forms  of  the  parasite. 

Fig.  44.  —  Tangential  section  of  an  artery,  skin  of  scrotum,  Human 
Case  IV.,  showing  a  smooth  muscle  fiber  filled  with  the  lanceolate  form  of 
the  parasite.     Photomicrograph,  2,000  diameters. 

Plate  X.,  Fig.  45.  —  Section,  Guinea  Pig  11,  Strain  I.,  to  show  the 
perivascular  accumulation  of  large  mononuclear  cells,  an  arteriole  from  the 
epididymis. 

Fig.  46.  — ■  The  lumen  of  the  arteriole  of  Fig.  45,  showing  smooth  muscle 
fibers  filled  with  the  parasites.     2,000  diameters. 

Plate  XI.,  Fig.  47.  —  Section  of  a  vein  of  the  skin  from  a  monkey, 
showing  acute  thrombosis  and  distribution  of  the  parasites.  1,000  di- 
ameters. 

Fig.  48.  —  Section  of  an  arteriole  of  the  skin,  Guinea  Pig  11,  Strain  I., 
showing  smooth  muscle  fibers  containing  the  lanceolate  form  of  the  para- 
site.    2,000  diameters. 

Plate  XII.,  Fig.  49.  —  Section  of  an  arteriole  of  the  skin  of  the  scro- 
tum of  a  guinea-pig,  showing  occlusion  due  to  endothelial  cell  proliferation. 
1,000  diameters. 


196  WOLBACH. 

Fig.  50.  —  Parasites  in  the  intima  of  an  artery  of  the  testes,  Monkey  i. 
1,500  diameters. 

Plate  XIII.,  Fig.  51.  —  Longitudinal  section  of  an  artery  of  the  epi- 
didymis, Human  Case  III.,  Giemsa's  stain,  125  diameters.  Beginning 
thrombus  formation. 

Fig.  52.  —  Guinea  Pig  29,  Tick  X.  strain  series.  The  scrotal  lesion, 
with  beginning  necrosis. 

Plate  XIV.,  Fig.  53.  —  Skin  of  leg,  Case  I.,  showing  vascular  lesions. 
Fig.  54.  —  Skin  of  buttock.  Case  I.,  showing  vascular  lesions. 
Fig.  55.  —  Skin  of  thigh,  Case  II.,  showing  vascular  lesions. 

Plate  XV.,  Fig.  56.  ■ — Parasites  in  mononuclear  cell  (endothelial  cell) 
in  blood  film,  Human  Case  II.     Photomicrograph  2,000  diameters. 

Fig.  57. — Arteriole,  skin.  Case  I.,  showing  perivascular  infiltration 
and  mural  thrombus. 

Fig.  58. — Arteriole,  epididymis,  Human  Case  III. 

Plate  XVI.,  Fig.  59.  —  Section  through  tick  bite,  Hayes  Guinea  Pig 
3,  showing  lanceolate  form  of  parasite  in  endothelial  cells  in  oedematous 
connective  tissue.     Giemsa's  stain,  1,500  diameters. 

Fig.  60.  —  Intima  of  an  artery  of  the  skin  from  the  ankle  of  Human 
Case  II.,  showing  early  thrombosis  and  a  group  of  the  parasites  in  an  endo- 
thelial cell. 

Plate  XVII.,  Fig.  61.  —  Liver,  Human  Case  II.,  showing  focal  necrosis, 
1,000  diameters. 

Fig.  62.  — Spleen,  Human  Case  II.,  1,000  diameters. 

Plate  XVIII.,  Fig.  63.  —  Artery,  testes.  Human  Case  HI.,  showing 
early  lesions,  with  parasites  in  endothelium  and  beneath  internal  elastica. 
1,000  diameters. 

Fig.  64.  — Arteriole  of  skin,  Guinea  Pig  11,  Strain  I.     2,000  diameters. 

Fig.  65.  — Artery,  skin.  Monkey  I,  showing  early  lesions  and  the  para- 
sites beneath  internal  elastica.     1,000  diameters. 

Plate  XIX.,  Fig.  66.  —  Arteriole,  skin  of  scrotum.  Human  Case  II., 
Giemsa's  stain,  showing  distribution  of  the  parasites  and  early  reaction. 
1,500  diameters. 

Fig.  67.  —  Section  through  alveolar  wall  of  lung.  Case  II.,  to  show  the 
accumulation  of  endothelial  cells.     750  diameters. 

Fig.  68.  —  Parasites  in  smooth  muscle  fibers.  From  a  tangentially- 
cut  section  of  an  artery  of  the  testes.  Human  Case  II. 

Plate  XX.,  Fig.  69.  —  Artery,  skin,  Guinea  Pig  10,  Strain  I.,  showsthe 
parasites  in  smooth  muscle  fibers.  Photomicrograph  reduced  from  2,000 
diameters. 

Plate  XXI.,  Fig.  70.  —  Artery,  skin  of  scrotum.  Human  Case  HI., 
showing  endothelial  proliferation  and  a  smooth  muscle  fiber  containing 
the  parasites.     Photomicrograph  reduced  from  2,000  diameters. 


ROCKY    MOUNTAIN    SPOTTED    FEVER.  I97 

ACKNOWLEDGMENTS. 

For  the  suggestion  and  invitation  to  study  the  disease  in  the  Bitter 
Root  Valley  and  for  traveling  expenses  I  am  indebted  to  the  Montana 
Department  of  Health  and  the  Montana  State  Board  of  Entomology. 
It  gives  me  pleasure  to  express  my  thanks  and  indebtedness  to  the  follow- 
ing gentlemen: 

To  Prof.  R.  A.  Cooley,  state  entomologist  and  secretary  of  the  Board 
of  Entomology,  and  Dr.  W.  F.  Cogswell,  secretary  of  the  State  Board  of 
Health  of  Montana  and  chairman  of  the  Board  of  Entomology,  for  many 
kindnesses;  to  Drs.  H.  C.  Smith,  F.  D.  Pease,  and  W.  H.  Harrison  of 
Missoula  for  very  generous  and  self-sacrificing  provision  of  laboratory 
facilities;  to  Surgeon  L.  D.  Fricks  of  the  Public  Health  Service  for  ticks 
and  strains  of  the  virus;  to  W.  V.  King,  Ph.D.,  U.  S.  Bureau  of  Ento- 
mology, for  friendly  assistance  and  ticks;  to  R.  R.  Parker,  Ph.D.,  of  the 
Montana  State  Board  of  Entomology,  for  ticks;  to  Dr.  N.  C.  Foot,  for 
assistance  in  maintaining  the  virus  in  guinea-pigs;  to  Dr.  F.  D.  Pease  of 
Missoula,  Dr.  Fritz  E.  Buchen  and  Dr.  R.  F.  Owens  of  Hamilton,  and 
Dr.  W.  T.  Thornton  of  Stevensville,  for  the  opportunity  of  studying  cases, 
and  much  assistance. 

The  drawings  were  made  by  Miss  Etta  R.  Piotti,  with  the  remarkable 
accuracy  characteristic  of  her  work. 


The  Journal  of  Medical  Research,  Vol.  XLI.,  No.  i,  November,  1919- 


Journal  of  Medical  Research. 


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